diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5c8abb8b4..95e86b239 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -12,12 +12,12 @@ jobs:
   unit-tests-single:
     uses: ./.github/workflows/unit-tests.yml
     with:
-      cmake-args: '-UNUMBER_OF_WORKERS -DLF_UNTHREADED=1'
+      cmake-args: '-UNUMBER_OF_WORKERS -DLF_SINGLE_THREADED=1'
 
   unit-tests-multi:
     uses: ./.github/workflows/unit-tests.yml
     with:
-      cmake-args: '-DNUMBER_OF_WORKERS=4 -DLF_THREADED=1'
+      cmake-args: '-DNUMBER_OF_WORKERS=4 -ULF_SINGLE_THREADED'
 
   build-rti:
     uses: ./.github/workflows/build-rti.yml
diff --git a/CMakeLists.txt b/CMakeLists.txt
index c675a3f53..9eadfeda2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -15,13 +15,11 @@ if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
     set(CMAKE_BUILD_TYPE ${DEFAULT_BUILD_TYPE} CACHE STRING "Choose the type of build." FORCE)
 endif()
 
-# Whether or not we are using THREADED or UNTHREADEd runtime is a global
+# Whether or not we are using THREADED or SINGLE-THREADED runtime is a global
 # flag. If it is passed to cmake. Then add it as a global compile def which
 # is inherited by all child nodes (add_subdirectory)
-if(DEFINED LF_THREADED)
-    add_compile_definitions(LF_THREADED=1)
-else()
-    add_compile_definitions(LF_UNTHREADED=1)
+if(DEFINED LF_SINGLE_THREADED)
+    add_compile_definitions(LF_SINGLE_THREADED=1)
 endif()
 
 set(Test test)
diff --git a/core/CMakeLists.txt b/core/CMakeLists.txt
index a9026392c..16bf0e616 100644
--- a/core/CMakeLists.txt
+++ b/core/CMakeLists.txt
@@ -15,22 +15,22 @@ list(APPEND INFO_SOURCES ${GENERAL_SOURCES})
 # Create the core library
 add_library(core ${GENERAL_SOURCES})
 
-# Add sources for either threaded or unthreaded runtime
+# Add sources for either threaded or single-threaded runtime
 if (DEFINED FEDERATED)
     include(federated/CMakeLists.txt)
 endif()
 
-# Add sources for either threaded or unthreaded runtime
-if(DEFINED LF_THREADED)
+# Add sources for either threaded or single-threaded runtime
+if(DEFINED LF_SINGLE_THREADED)
+    message(STATUS "Including sources for single-threaded runtime.")
+    list(APPEND SINGLE_THREADED_SOURCES reactor.c)
+    target_sources(core PRIVATE ${SINGLE_THREADED_SOURCES})
+    list(APPEND INFO_SOURCES ${SINGLE_THREADED_SOURCES})
+else()
     message(STATUS "Including sources for threaded runtime with \
 ${NUMBER_OF_WORKERS} worker(s) with scheduler=${SCHEDULER} and \
 tracing=${LF_TRACE}.")
     include(threaded/CMakeLists.txt)
-else()
-    message(STATUS "Including sources for unthreaded runtime.")
-    list(APPEND SINGLE_THREADED_SOURCES reactor.c)
-    target_sources(core PRIVATE ${SINGLE_THREADED_SOURCES})
-    list(APPEND INFO_SOURCES ${SINGLE_THREADED_SOURCES})
 endif()
 
 
@@ -75,7 +75,7 @@ if(DEFINED _LF_CLOCK_SYNC_ON)
 endif()
 
 # Link with thread library, unless if we are targeting the Zephyr RTOS
-if(DEFINED LF_THREADED OR DEFINED LF_TRACE)
+if(NOT DEFINED LF_SINGLE_THREADED OR DEFINED LF_TRACE)
     if(NOT ${CMAKE_SYSTEM_NAME} STREQUAL "Zephyr")
         find_package(Threads REQUIRED)
         target_link_libraries(core PUBLIC Threads::Threads)
@@ -112,9 +112,8 @@ define(FEDERATED_DECENTRALIZED)
 define(FEDERATED)
 define(FEDERATED_AUTHENTICATED)
 define(LF_REACTION_GRAPH_BREADTH)
-define(LF_THREADED)
 define(LF_TRACE)
-define(LF_UNTHREADED)
+define(LF_SINGLE_THREADED)
 define(LOG_LEVEL)
 define(MODAL_REACTORS)
 define(NUMBER_OF_FEDERATES)
diff --git a/core/environment.c b/core/environment.c
index 4216800dc..4ca79c11e 100644
--- a/core/environment.c
+++ b/core/environment.c
@@ -34,7 +34,7 @@
 #include "lf_types.h"
 #include <string.h>
 #include "trace.h"
-#ifdef LF_THREADED
+#if !defined(LF_SINGLE_THREADED)
 #include "scheduler.h"
 #endif
 
@@ -42,7 +42,7 @@
  * @brief Initialize the threaded part of the environment struct.
  */
 static void environment_init_threaded(environment_t* env, int num_workers) {
-#ifdef LF_THREADED
+#if !defined(LF_SINGLE_THREADED)
     env->num_workers = num_workers;
     env->thread_ids = (lf_thread_t*)calloc(num_workers, sizeof(lf_thread_t));
     lf_assert(env->thread_ids != NULL, "Out of memory");
@@ -64,10 +64,10 @@ static void environment_init_threaded(environment_t* env, int num_workers) {
 #endif
 }
 /**
- * @brief Initialize the unthreaded-specific parts of the environment struct.
+ * @brief Initialize the single-threaded-specific parts of the environment struct.
  */
-static void environment_init_unthreaded(environment_t* env) {
-#ifdef LF_UNTHREADED
+static void environment_init_single_threaded(environment_t* env) {
+#ifdef LF_SINGLE_THREADED
     // Reaction queue ordered first by deadline, then by level.
     // The index of the reaction holds the deadline in the 48 most significant bits,
     // the level in the 16 least significant bits.
@@ -126,14 +126,14 @@ void environment_init_tags( environment_t *env, instant_t start_time, interval_t
 }
 
 static void environment_free_threaded(environment_t* env) {
-#ifdef LF_THREADED
+#if !defined(LF_SINGLE_THREADED)
     free(env->thread_ids);
     lf_sched_free(env->scheduler);   
 #endif
 }
 
-static void environment_free_unthreaded(environment_t* env) {
-#ifdef LF_UNTHREADED
+static void environment_free_single_threaded(environment_t* env) {
+#ifdef LF_SINGLE_THREADED
     pqueue_free(env->reaction_q);
 #endif
 }
@@ -166,7 +166,7 @@ void environment_free(environment_t* env) {
     pqueue_free(env->next_q);
 
     environment_free_threaded(env);
-    environment_free_unthreaded(env);
+    environment_free_single_threaded(env);
     environment_free_modes(env);
     environment_free_federated(env);
     trace_free(env->trace);
@@ -230,7 +230,7 @@ int environment_init(
 
     // Initialize functionality depending on target properties.
     environment_init_threaded(env, num_workers);
-    environment_init_unthreaded(env);
+    environment_init_single_threaded(env);
     environment_init_modes(env, num_modes, num_state_resets);
     environment_init_federated(env, num_is_present_fields);
 
diff --git a/core/federated/RTI/CMakeLists.txt b/core/federated/RTI/CMakeLists.txt
index c43dd70f3..b0fb5a326 100644
--- a/core/federated/RTI/CMakeLists.txt
+++ b/core/federated/RTI/CMakeLists.txt
@@ -79,8 +79,8 @@ IF(CMAKE_BUILD_TYPE MATCHES DEBUG)
     target_compile_definitions(RTI PUBLIC LOG_LEVEL=4)
 ENDIF(CMAKE_BUILD_TYPE MATCHES DEBUG)
 
-# Set LF_THREADING to get the threaded support and FEDERATED to get federated compilation support
-target_compile_definitions(RTI PUBLIC LF_THREADED=1 FEDERATED=1)
+# Set FEDERATED to get federated compilation support
+target_compile_definitions(RTI PUBLIC FEDERATED=1)
 target_compile_definitions(RTI PUBLIC PLATFORM_${CMAKE_SYSTEM_NAME})
 
 # Set RTI Tracing
diff --git a/core/platform/arduino_mbed/ConditionWrapper.cpp b/core/platform/arduino_mbed/ConditionWrapper.cpp
index 1e2a8f4ed..6fe3e4422 100644
--- a/core/platform/arduino_mbed/ConditionWrapper.cpp
+++ b/core/platform/arduino_mbed/ConditionWrapper.cpp
@@ -27,7 +27,7 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *  @author{Anirudh Rengarajan <arengarajan@berkeley.edu>}
  */
 
-#if defined(LF_THREADED)
+#if !defined(LF_SINGLE_THREADED)
 #include "mbed.h"
 #include "MutexWrapper.h"
 
diff --git a/core/platform/arduino_mbed/MutexWrapper.cpp b/core/platform/arduino_mbed/MutexWrapper.cpp
index fa507e31b..3f3165326 100644
--- a/core/platform/arduino_mbed/MutexWrapper.cpp
+++ b/core/platform/arduino_mbed/MutexWrapper.cpp
@@ -27,7 +27,7 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *  @author{Anirudh Rengarajan <arengarajan@berkeley.edu>}
  */
 
-#if defined(LF_THREADED)
+#if !defined(LF_SINGLE_THREADED)
 #include "mbed.h"
 #include "rtos.h"
 using namespace rtos;
diff --git a/core/platform/arduino_mbed/ThreadWrapper.cpp b/core/platform/arduino_mbed/ThreadWrapper.cpp
index 2b7824606..eaa19ae1e 100644
--- a/core/platform/arduino_mbed/ThreadWrapper.cpp
+++ b/core/platform/arduino_mbed/ThreadWrapper.cpp
@@ -27,7 +27,7 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *  @author{Anirudh Rengarajan <arengarajan@berkeley.edu>}
  */
 
-#if defined(LF_THREADED)
+#if !defined(LF_SINGLE_THREADED)
 #include "mbed.h"
 #include "rtos.h"
 
diff --git a/core/platform/lf_C11_threads_support.c b/core/platform/lf_C11_threads_support.c
index c0862f742..de3320dd0 100644
--- a/core/platform/lf_C11_threads_support.c
+++ b/core/platform/lf_C11_threads_support.c
@@ -1,4 +1,4 @@
-#if defined(LF_THREADED) && !defined(PLATFORM_ARDUINO)
+#if !defined(LF_SINGLE_THREADED) && !defined(PLATFORM_ARDUINO)
 #include "platform.h"
 #include "lf_C11_threads_support.h"
 
diff --git a/core/platform/lf_POSIX_threads_support.c b/core/platform/lf_POSIX_threads_support.c
index 180cde8cd..8b505acb5 100644
--- a/core/platform/lf_POSIX_threads_support.c
+++ b/core/platform/lf_POSIX_threads_support.c
@@ -1,4 +1,4 @@
-#if defined(LF_THREADED) && !defined(PLATFORM_ARDUINO)
+#if !defined(LF_SINGLE_THREADED) && !defined(PLATFORM_ARDUINO)
 #include "platform.h"
 #include "lf_POSIX_threads_support.h"
 
diff --git a/core/platform/lf_arduino_support.c b/core/platform/lf_arduino_support.c
index bf1ac9483..57c28d1ec 100644
--- a/core/platform/lf_arduino_support.c
+++ b/core/platform/lf_arduino_support.c
@@ -125,7 +125,7 @@ int _lf_clock_now(instant_t* t) {
     return 0;
 }
 
-#if defined(LF_UNTHREADED)
+#if defined(LF_SINGLE_THREADED)
 
 int lf_enable_interrupts_nested() {
     if (_lf_num_nested_critical_sections++ == 0) {
@@ -152,7 +152,7 @@ int lf_disable_interrupts_nested() {
  * Handle notifications from the runtime of changes to the event queue.
  * If a sleep is in progress, it should be interrupted.
 */
-int _lf_unthreaded_notify_of_event() {
+int _lf_single_threaded_notify_of_event() {
    _lf_async_event = true;
    return 0;
 }
diff --git a/core/platform/lf_linux_support.c b/core/platform/lf_linux_support.c
index 3bb5077c8..046415df6 100644
--- a/core/platform/lf_linux_support.c
+++ b/core/platform/lf_linux_support.c
@@ -39,11 +39,11 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #define LF_MAX_SLEEP_NS USEC(UINT64_MAX)
 #define LF_MIN_SLEEP_NS USEC(10)
 
-#if defined LF_UNTHREADED
+#if defined LF_SINGLE_THREADED
     #include "lf_os_single_threaded_support.c"
 #endif
 
-#if defined LF_THREADED
+#if !defined LF_SINGLE_THREADED
     #if __STDC_VERSION__ < 201112L || defined (__STDC_NO_THREADS__)
         // (Not C++11 or later) or no threads support
         #include "lf_POSIX_threads_support.c"
diff --git a/core/platform/lf_macos_support.c b/core/platform/lf_macos_support.c
index 93908a6dd..fcc958c8a 100644
--- a/core/platform/lf_macos_support.c
+++ b/core/platform/lf_macos_support.c
@@ -35,11 +35,11 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include "tag.h"
 #define LF_MIN_SLEEP_NS USEC(10)
 
-#if defined LF_UNTHREADED
+#if defined LF_SINGLE_THREADED
     #include "lf_os_single_threaded_support.c"
 #endif
 
-#if defined LF_THREADED
+#if !defined LF_SINGLE_THREADED
     #if __STDC_VERSION__ < 201112L || defined (__STDC_NO_THREADS__)
         // (Not C++11 or later) or no threads support
         #include "lf_POSIX_threads_support.c"
diff --git a/core/platform/lf_nrf52_support.c b/core/platform/lf_nrf52_support.c
index 3928b06db..61dcc101b 100644
--- a/core/platform/lf_nrf52_support.c
+++ b/core/platform/lf_nrf52_support.c
@@ -285,7 +285,7 @@ int lf_disable_interrupts_nested() {
  * 
  * @return int 
  */
-int _lf_unthreaded_notify_of_event() {
+int _lf_single_threaded_notify_of_event() {
     _lf_async_event = true;
     return 0;
 }
diff --git a/core/platform/lf_os_single_threaded_support.c b/core/platform/lf_os_single_threaded_support.c
index dc4c4e8f5..1306d4c17 100644
--- a/core/platform/lf_os_single_threaded_support.c
+++ b/core/platform/lf_os_single_threaded_support.c
@@ -1,4 +1,4 @@
-#if defined LF_UNTHREADED && !defined(PLATFORM_ARDUINO)
+#if defined LF_SINGLE_THREADED && !defined(PLATFORM_ARDUINO)
 /**
  * @file lf_os_single_threaded_support.c
  * @author Marten Lohstroh (marten@berkeley.edu)
@@ -16,7 +16,7 @@
 #endif
 
 /**
- * @brief Unthreaded support under a OS is a special case in which we assume
+ * @brief Single-threaded support under a OS is a special case in which we assume
  * only a single execution context. Other threads scheduling physical actions
  * are not a use-case. ISRs scheduling physical actions are also not a use-case.
  * 
@@ -30,7 +30,7 @@ int lf_enable_interrupts_nested() {
     return 0;
 }
 
-int _lf_unthreaded_notify_of_event() {
+int _lf_single_threaded_notify_of_event() {
     return 0;
 }
 
diff --git a/core/platform/lf_rp2040_support.c b/core/platform/lf_rp2040_support.c
index 8cbc0985e..045c6d6d9 100644
--- a/core/platform/lf_rp2040_support.c
+++ b/core/platform/lf_rp2040_support.c
@@ -31,6 +31,10 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  * @author{Abhi Gundrala <gundralaa@berkeley.edu>}
  */
 
+#if !defined(LF_SINGLE_THREADED)
+#error "Only the single-threaded runtime has support for RP2040"
+#endif
+
 #include "lf_rp2040_support.h"
 #include "platform.h"
 #include "utils/util.h"
@@ -59,7 +63,7 @@ static uint32_t _lf_num_nested_crit_sec = 0;
 
 /**
  * Initialize basic runtime infrastructure and 
- * synchronization structs for an unthreaded runtime.
+ * synchronization structs for an single-threaded runtime.
  */
 void _lf_initialize_clock(void) {
     // init stdio lib
@@ -113,8 +117,8 @@ int lf_sleep(interval_t sleep_duration) {
  * by the argument or return early if the binary 
  * _lf_sem_irq_event semaphore is released before the target time.
  *
- * The semaphore is released using the _lf_unthreaded_notify_of_event
- * which is called by lf_schedule in the unthreaded runtime for physical actions.
+ * The semaphore is released using the _lf_single_threaded_notify_of_event
+ * which is called by lf_schedule in the single_threaded runtime for physical actions.
  *
  * @param  env  pointer to environment struct this runs in.
  * @param  wakeup_time  time in nanoseconds since boot to sleep until.
@@ -145,7 +149,7 @@ int _lf_interruptable_sleep_until_locked(environment_t* env, instant_t wakeup_ti
     return ret_code;
 }
 
-#ifdef LF_UNTHREADED
+#if defined(LF_SINGLE_THREADED)
 /**
  * The single thread RP2040 platform support treats second core
  * routines similar to external interrupt routine threads.
@@ -205,16 +209,13 @@ int lf_enable_interrupts_nested() {
  *
  * @return error code or 0 on success
  */
-int _lf_unthreaded_notify_of_event() {
+int _lf_single_threaded_notify_of_event() {
     // notify main sleep loop of event
     sem_release(&_lf_sem_irq_event);
     return 0;
 }
-#endif //LF_UNTHREADED
+#endif // LF_SINGLE_THREADED
 
-#ifdef LF_THREADED
-#error "Threading for baremetal RP2040 not supported"
-#endif //LF_THREADED
 
 #endif // PLATFORM_RP2040
 
diff --git a/core/platform/lf_windows_support.c b/core/platform/lf_windows_support.c
index b1ec9b20a..f38828505 100644
--- a/core/platform/lf_windows_support.c
+++ b/core/platform/lf_windows_support.c
@@ -158,12 +158,12 @@ int lf_nanosleep(interval_t sleep_duration) {
     return lf_sleep(sleep_duration);
 }
 
-#if defined(LF_UNTHREADED)
+#if defined(LF_SINGLE_THREADED)
 #include "lf_os_single_threaded_support.c"
 #endif
 
 
-#if defined(LF_THREADED)
+#if !defined(LF_SINGLE_THREADED)
 int lf_available_cores() {
     SYSTEM_INFO sysinfo;
     GetSystemInfo(&sysinfo);
diff --git a/core/platform/lf_zephyr_clock_counter.c b/core/platform/lf_zephyr_clock_counter.c
index e292e2715..f6110b19b 100644
--- a/core/platform/lf_zephyr_clock_counter.c
+++ b/core/platform/lf_zephyr_clock_counter.c
@@ -210,7 +210,7 @@ int _lf_interruptable_sleep_until_locked(environment_t* env, instant_t wakeup) {
 /**
  * We notify of async events by setting the flag and giving the semaphore.
  */
-int _lf_unthreaded_notify_of_event() {
+int _lf_single_threaded_notify_of_event() {
    async_event = true;
     k_sem_give(&semaphore);
    return 0;
diff --git a/core/platform/lf_zephyr_clock_kernel.c b/core/platform/lf_zephyr_clock_kernel.c
index fae932742..281cfe3db 100644
--- a/core/platform/lf_zephyr_clock_kernel.c
+++ b/core/platform/lf_zephyr_clock_kernel.c
@@ -94,7 +94,7 @@ int _lf_interruptable_sleep_until_locked(environment_t* env, instant_t wakeup) {
  * Asynchronous events are notified by setting a flag which breaks the sleeping
  * thread out of the busy-wait.
  */
-int _lf_unthreaded_notify_of_event() {
+int _lf_single_threaded_notify_of_event() {
    async_event = true;
    return 0;
 }
diff --git a/core/platform/lf_zephyr_support.c b/core/platform/lf_zephyr_support.c
index db77d6d88..1e10020b6 100644
--- a/core/platform/lf_zephyr_support.c
+++ b/core/platform/lf_zephyr_support.c
@@ -74,8 +74,7 @@ int lf_enable_interrupts_nested() {
     return 0;
 }
 
-#if defined(LF_THREADED)
-
+#if !defined(LF_SINGLE_THREADED)
 #if !defined(LF_ZEPHYR_STACK_SIZE)
     #define LF_ZEPHYR_STACK_SIZE LF_ZEPHYR_STACK_SIZE_DEFAULT
 #endif
diff --git a/core/reactor.c b/core/reactor.c
index b30632366..a41a0847d 100644
--- a/core/reactor.c
+++ b/core/reactor.c
@@ -1,4 +1,4 @@
-#if defined(LF_UNTHREADED)
+#if defined(LF_SINGLE_THREADED)
 /* Runtime infrastructure for the non-threaded version of the C target of Lingua Franca. */
 
 /*************
@@ -114,7 +114,7 @@ void lf_print_snapshot(environment_t* env) {
  * @param reaction The reaction.
  * @param worker_number The ID of the worker that is making this call. 0 should be
  *  used if there is only one worker (e.g., when the program is using the
- *  unthreaded C runtime). -1 is used for an anonymous call in a context where a
+ *  single-threaded C runtime). -1 is used for an anonymous call in a context where a
  *  worker number does not make sense (e.g., the caller is not a worker thread).
  */
 void _lf_trigger_reaction(environment_t* env, reaction_t* reaction, int worker_number) {
@@ -195,7 +195,7 @@ int _lf_do_step(environment_t* env) {
 
         if (!violation) {
             // Invoke the reaction function.
-            _lf_invoke_reaction(env, reaction, 0);   // 0 indicates unthreaded.
+            _lf_invoke_reaction(env, reaction, 0);   // 0 indicates single-threaded.
 
             // If the reaction produced outputs, put the resulting triggered
             // reactions into the queue.
@@ -365,7 +365,7 @@ int lf_reactor_c_main(int argc, const char* argv[]) {
         environment_t *env;
         int num_environments = _lf_get_environments(&env);
         lf_assert(num_environments == 1,
-            "Found %d environments. Only 1 can be used with the unthreaded runtime", num_environments);
+            "Found %d environments. Only 1 can be used with the single-threaded runtime", num_environments);
         
         LF_PRINT_DEBUG("Initializing.");
         initialize_global();
@@ -398,8 +398,12 @@ int lf_reactor_c_main(int argc, const char* argv[]) {
     }
 }
 
+/**
+ * @brief Notify of new event by calling the single-threaded platform API
+ * @param env Environment in which we are executing.
+ */
 int lf_notify_of_event(environment_t* env) {
-    return _lf_unthreaded_notify_of_event();
+    return _lf_single_threaded_notify_of_event();
 }
 
 int lf_critical_section_enter(environment_t* env) {
diff --git a/core/reactor_common.c b/core/reactor_common.c
index b7a3c9ac7..5422d1453 100644
--- a/core/reactor_common.c
+++ b/core/reactor_common.c
@@ -61,7 +61,7 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include "hashset/hashset_itr.h"
 #include "environment.h"
 
-#ifdef LF_THREADED
+#if !defined(LF_SINGLE_THREADED)
 #include "watchdog.h"
 
 // Code generated global variables.
@@ -253,7 +253,7 @@ void lf_set_stp_offset(interval_t offset) {
  * @param reaction The reaction.
  * @param worker_number The ID of the worker that is making this call. 0 should be
  *  used if there is only one worker (e.g., when the program is using the
- *  unthreaded C runtime). -1 is used for an anonymous call in a context where a
+ *  single-threaded C runtime). -1 is used for an anonymous call in a context where a
  *  worker number does not make sense (e.g., the caller is not a worker thread).
  */
 void _lf_trigger_reaction(environment_t* env, reaction_t* reaction, int worker_number);
@@ -1334,12 +1334,12 @@ trigger_handle_t _lf_schedule_int(lf_action_base_t* action, interval_t extra_del
  *
  * @param env Environment in which we are executing.
  * @param reaction The reaction that has just executed.
- * @param worker The thread number of the worker thread or 0 for unthreaded execution (for tracing).
+ * @param worker The thread number of the worker thread or 0 for single-threaded execution (for tracing).
  */
 void _lf_invoke_reaction(environment_t* env, reaction_t* reaction, int worker) {
     assert(env != GLOBAL_ENVIRONMENT);
 
-#ifdef LF_THREADED
+#if !defined(LF_SINGLE_THREADED)
     if (((self_base_t*) reaction->self)->reactor_mutex != NULL) {
         lf_mutex_lock((lf_mutex_t*)((self_base_t*)reaction->self)->reactor_mutex);
     }
@@ -1352,7 +1352,7 @@ void _lf_invoke_reaction(environment_t* env, reaction_t* reaction, int worker) {
     tracepoint_reaction_ends(env->trace, reaction, worker);
 
 
-#ifdef LF_THREADED
+#if !defined(LF_SINGLE_THREADED)
     if (((self_base_t*) reaction->self)->reactor_mutex != NULL) {
         lf_mutex_unlock((lf_mutex_t*)((self_base_t*)reaction->self)->reactor_mutex);
     }
@@ -1366,7 +1366,7 @@ void _lf_invoke_reaction(environment_t* env, reaction_t* reaction, int worker) {
  * the lock only when it actually inserts something onto the reaction queue.
  * @param env Environment in which we are executing.
  * @param reaction The reaction that has just executed.
- * @param worker The thread number of the worker thread or 0 for unthreaded execution (for tracing).
+ * @param worker The thread number of the worker thread or 0 for single-threaded execution (for tracing).
  */
 void schedule_output_reactions(environment_t *env, reaction_t* reaction, int worker) {
     assert(env != GLOBAL_ENVIRONMENT);
@@ -1796,7 +1796,7 @@ void termination(void) {
         lf_print_warning("Memory allocated for tokens has not been freed!");
         lf_print_warning("Number of unfreed tokens: %d.", _lf_count_token_allocations);
     }
-#ifdef LF_THREADED
+#if !defined(LF_SINGLE_THREADED)
     for (int i = 0; i < _lf_watchdog_count; i++) {
         if (_lf_watchdogs[i].base->reactor_mutex != NULL) {
             free(_lf_watchdogs[i].base->reactor_mutex);
diff --git a/core/threaded/reactor_threaded.c b/core/threaded/reactor_threaded.c
index 66ea0fe32..749550bc3 100644
--- a/core/threaded/reactor_threaded.c
+++ b/core/threaded/reactor_threaded.c
@@ -30,7 +30,7 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *  @author{Marten Lohstroh <marten@berkeley.edu>}
  *  @author{Soroush Bateni <soroush@utdallas.edu>}
  */
-#if defined LF_THREADED
+#if !defined LF_SINGLE_THREADED
 #ifndef NUMBER_OF_WORKERS
 #define NUMBER_OF_WORKERS 1
 #endif // NUMBER_OF_WORKERS
@@ -634,7 +634,7 @@ void lf_request_stop() {
  * @param reaction The reaction.
  * @param worker_number The ID of the worker that is making this call. 0 should be
  *  used if there is only one worker (e.g., when the program is using the
- *  unthreaded C runtime). -1 is used for an anonymous call in a context where a
+ *  single-threaded C runtime). -1 is used for an anonymous call in a context where a
  *  worker number does not make sense (e.g., the caller is not a worker thread).
  */
 void _lf_trigger_reaction(environment_t* env, reaction_t* reaction, int worker_number) {
diff --git a/core/threaded/scheduler_GEDF_NP.c b/core/threaded/scheduler_GEDF_NP.c
index 7b16021ec..e45763ea7 100644
--- a/core/threaded/scheduler_GEDF_NP.c
+++ b/core/threaded/scheduler_GEDF_NP.c
@@ -355,7 +355,7 @@ void lf_sched_done_with_reaction(size_t worker_number,
  * @param reaction The reaction to trigger at the current tag.
  * @param worker_number The ID of the worker that is making this call. 0 should
  * be used if there is only one worker (e.g., when the program is using the
- *  unthreaded C runtime). -1 is used for an anonymous call in a context where a
+ *  single-threaded C runtime). -1 is used for an anonymous call in a context where a
  *  worker number does not make sense (e.g., the caller is not a worker thread).
  */
 void lf_scheduler_trigger_reaction(lf_scheduler_t* scheduler, reaction_t* reaction, int worker_number) {
diff --git a/core/threaded/scheduler_NP.c b/core/threaded/scheduler_NP.c
index bfa25f084..a9310aa2f 100644
--- a/core/threaded/scheduler_NP.c
+++ b/core/threaded/scheduler_NP.c
@@ -1,4 +1,4 @@
-#if defined(LF_THREADED)
+#if !defined(LF_SINGLE_THREADED)
 /* Non-preemptive scheduler for the threaded runtime of the C target of Lingua
 Franca. */
 
@@ -37,7 +37,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  * @author{Marten Lohstroh <marten@berkeley.edu>}
  */
 #include "lf_types.h"
-#if SCHEDULER == SCHED_NP || (!defined(SCHEDULER) && defined(LF_THREADED))
+#if SCHEDULER == SCHED_NP || !defined(SCHEDULER)
 #ifndef NUMBER_OF_WORKERS
 #define NUMBER_OF_WORKERS 1
 #endif  // NUMBER_OF_WORKERS
@@ -432,7 +432,7 @@ void lf_sched_done_with_reaction(size_t worker_number,
  * @param reaction The reaction to trigger at the current tag.
  * @param worker_number The ID of the worker that is making this call. 0 should
  *  be used if there is only one worker (e.g., when the program is using the
- *  unthreaded C runtime). -1 is used for an anonymous call in a context where a
+ *  single-threaded C runtime). -1 is used for an anonymous call in a context where a
  *  worker number does not make sense (e.g., the caller is not a worker thread).
  *
  */
diff --git a/core/threaded/scheduler_sync_tag_advance.c b/core/threaded/scheduler_sync_tag_advance.c
index cdaff6d21..4c68a623a 100644
--- a/core/threaded/scheduler_sync_tag_advance.c
+++ b/core/threaded/scheduler_sync_tag_advance.c
@@ -1,4 +1,4 @@
-#if defined(LF_THREADED)
+#if !defined(LF_SINGLE_THREADED)
 /*************
 Copyright (c) 2022, The University of Texas at Dallas.
 Copyright (c) 2022, The University of California at Berkeley.
diff --git a/core/trace.c b/core/trace.c
index 1e9703c09..1839e8f84 100644
--- a/core/trace.c
+++ b/core/trace.c
@@ -254,7 +254,7 @@ void start_trace(trace_t* trace) {
     trace->_lf_trace_header_written = false;
 
     // Allocate an array of arrays of trace records, one per worker thread plus one
-    // for the 0 thread (the main thread, or in an unthreaded program, the only
+    // for the 0 thread (the main thread, or in an single-threaded program, the only
     // thread).
     trace->_lf_number_of_trace_buffers = _lf_number_of_workers + 1;
     trace->_lf_trace_buffer = (trace_record_t**)malloc(sizeof(trace_record_t*) * trace->_lf_number_of_trace_buffers);
@@ -326,7 +326,7 @@ void tracepoint(
 /**
  * Trace the start of a reaction execution.
  * @param reaction Pointer to the reaction_t struct for the reaction.
- * @param worker The thread number of the worker thread or 0 for unthreaded execution.
+ * @param worker The thread number of the worker thread or 0 for single-threaded execution.
  */
 void tracepoint_reaction_starts(trace_t* trace, reaction_t* reaction, int worker) {
     tracepoint(trace, reaction_starts, reaction->self, NULL, worker, worker, reaction->number, NULL, NULL, 0, true);
@@ -335,7 +335,7 @@ void tracepoint_reaction_starts(trace_t* trace, reaction_t* reaction, int worker
 /**
  * Trace the end of a reaction execution.
  * @param reaction Pointer to the reaction_t struct for the reaction.
- * @param worker The thread number of the worker thread or 0 for unthreaded execution.
+ * @param worker The thread number of the worker thread or 0 for single-threaded execution.
  */
 void tracepoint_reaction_ends(trace_t* trace, reaction_t* reaction, int worker) {
     tracepoint(trace, reaction_ends, reaction->self, NULL, worker, worker, reaction->number, NULL, NULL, 0, false);
@@ -418,7 +418,7 @@ void tracepoint_user_value(void* self, char* description, long long value) {
 
 /**
  * Trace the start of a worker waiting for something to change on the event or reaction queue.
- * @param worker The thread number of the worker thread or 0 for unthreaded execution.
+ * @param worker The thread number of the worker thread or 0 for single-threaded execution.
  */
 void tracepoint_worker_wait_starts(trace_t* trace, int worker) {
     tracepoint(trace, worker_wait_starts, NULL, NULL, worker, worker, -1, NULL, NULL, 0, true);
@@ -426,7 +426,7 @@ void tracepoint_worker_wait_starts(trace_t* trace, int worker) {
 
 /**
  * Trace the end of a worker waiting for something to change on the event or reaction queue.
- * @param worker The thread number of the worker thread or 0 for unthreaded execution.
+ * @param worker The thread number of the worker thread or 0 for single-threaded execution.
  */
 void tracepoint_worker_wait_ends(trace_t* trace, int worker) {
     tracepoint(trace, worker_wait_ends, NULL, NULL, worker, worker, -1, NULL, NULL, 0, false);
@@ -451,7 +451,7 @@ void tracepoint_scheduler_advancing_time_ends(trace_t* trace) {
 /**
  * Trace the occurrence of a deadline miss.
  * @param reaction Pointer to the reaction_t struct for the reaction.
- * @param worker The thread number of the worker thread or 0 for unthreaded execution.
+ * @param worker The thread number of the worker thread or 0 for single-threaded execution.
  */
 void tracepoint_reaction_deadline_missed(trace_t* trace, reaction_t *reaction, int worker) {
     tracepoint(trace, reaction_deadline_missed, reaction->self, NULL, worker, worker, reaction->number, NULL, NULL, 0, false);
diff --git a/core/utils/semaphore.c b/core/utils/semaphore.c
index 87ce94443..244594762 100644
--- a/core/utils/semaphore.c
+++ b/core/utils/semaphore.c
@@ -1,4 +1,4 @@
-#if defined(LF_THREADED)
+#if !defined(LF_SINGLE_THREADED)
 /* Semaphore utility for reactor C. */
 
 /*************
diff --git a/include/core/environment.h b/include/core/environment.h
index ed93b72d2..db97d4f05 100644
--- a/include/core/environment.h
+++ b/include/core/environment.h
@@ -88,10 +88,9 @@ typedef struct environment_t {
     int reset_reactions_size;
     mode_environment_t* modes;
     trace_t* trace;
-#ifdef LF_UNTHREADED
+#if defined(LF_SINGLE_THREADED)
     pqueue_t *reaction_q;
-#endif 
-#ifdef LF_THREADED
+#else
     int num_workers;
     lf_thread_t* thread_ids;
     lf_mutex_t mutex;
@@ -99,14 +98,14 @@ typedef struct environment_t {
     lf_scheduler_t* scheduler;
     _lf_tag_advancement_barrier barrier;
     lf_cond_t global_tag_barrier_requestors_reached_zero;
-#endif // LF_THREADED
-#ifdef FEDERATED
+#endif // LF_SINGLE_THREADED
+#if defined(FEDERATED)
     tag_t** _lf_intended_tag_fields;
     int _lf_intended_tag_fields_size;
 #endif // FEDERATED
 } environment_t;
 
-#ifdef MODAL_REACTORS
+#if defined(MODAL_REACTORS)
 struct mode_environment_t {
     uint8_t triggered_reactions_request;
     reactor_mode_state_t** modal_reactor_states;
diff --git a/include/core/lf_types.h b/include/core/lf_types.h
index 6b7ad34d2..a48d445fc 100644
--- a/include/core/lf_types.h
+++ b/include/core/lf_types.h
@@ -298,11 +298,11 @@ typedef struct self_base_t {
 	struct allocation_record_t *allocations;
 	struct reaction_t *executing_reaction;   // The currently executing reaction of the reactor.
     environment_t * environment;
-#ifdef LF_THREADED
+#if !defined(LF_SINGLE_THREADED)
     void* reactor_mutex; // If not null, this is expected to point to an lf_mutex_t.
                           // It is not declared as such to avoid a dependence on platform.h.
 #endif
-#ifdef MODAL_REACTORS
+#if defined(MODAL_REACTORS)
     reactor_mode_state_t _lf__mode_state;    // The current mode (for modal models).
 #endif
 } self_base_t;
diff --git a/include/core/platform.h b/include/core/platform.h
index a32cfb516..defc67ecf 100644
--- a/include/core/platform.h
+++ b/include/core/platform.h
@@ -36,10 +36,6 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #ifndef PLATFORM_H
 #define PLATFORM_H
 
-#if defined(LF_THREADED) && defined(LF_UNTHREADED)
-#error LF_UNTHREADED and LF_THREADED runtime requested
-#endif
-
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -51,7 +47,7 @@ extern "C" {
 typedef struct environment_t environment_t;
 
 /**
- * @brief Notify of new event by calling the unthreaded platform API
+ * @brief Notify of new event.
  * @param env Environment in which we are executing.
  */
 int lf_notify_of_event(environment_t* env);
@@ -98,16 +94,13 @@ int lf_critical_section_exit(environment_t* env);
 #error "Platform not supported"
 #endif
 
-#if !defined(LF_THREADED)
-    typedef void lf_mutex_t;
-#endif
-
 #define LF_TIMEOUT 1
 
 
-// To support the unthreaded runtime, we need the following functions. They
+// To support the single-threaded runtime, we need the following functions. They
 //  are not required by the threaded runtime and is thus hidden behind a #ifdef.
-#if defined (LF_UNTHREADED)
+#if defined (LF_SINGLE_THREADED)
+    typedef void lf_mutex_t;
     /**
      * @brief Disable interrupts with support for nested calls
      * 
@@ -122,17 +115,14 @@ int lf_critical_section_exit(environment_t* env);
     int lf_enable_interrupts_nested();
 
     /**
-     * @brief Notify sleeping unthreaded context of new event
+     * @brief Notify sleeping single-threaded context of new event
      * 
      * @return int 
      */
-    int _lf_unthreaded_notify_of_event();
-#endif
-
-
+    int _lf_single_threaded_notify_of_event();
+#else 
 // For platforms with threading support, the following functions
 // abstract the API so that the LF runtime remains portable.
-#if defined LF_THREADED
 
 
 /**
diff --git a/include/core/platform/lf_arduino_support.h b/include/core/platform/lf_arduino_support.h
index 9685090c1..ad9adde1c 100644
--- a/include/core/platform/lf_arduino_support.h
+++ b/include/core/platform/lf_arduino_support.h
@@ -112,14 +112,14 @@ struct timespec {
 #endif
 #endif
 
-#ifdef LF_THREADED
+#if !defined(LF_SINGLE_THREADED)
 #warning "Threaded support on Arduino is still experimental"
 
 typedef void* lf_mutex_t;
 typedef void* lf_cond_t;
 typedef void* lf_thread_t;
 
-#endif // LF_THREADED
+#endif // !LF_SNIGLE_THREADED
 
 #define PRINTF_TIME "%" PRIu32
 #define PRINTF_MICROSTEP "%" PRIu32
diff --git a/include/core/platform/lf_linux_support.h b/include/core/platform/lf_linux_support.h
index 021b236db..17b01f134 100644
--- a/include/core/platform/lf_linux_support.h
+++ b/include/core/platform/lf_linux_support.h
@@ -39,7 +39,7 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 // Use 64-bit times and 32-bit unsigned microsteps
 #include "lf_tag_64_32.h"
 
-#if defined LF_THREADED
+#if !defined LF_SINGLE_THREADED
     #if __STDC_VERSION__ < 201112L || defined (__STDC_NO_THREADS__)
         // (Not C++11 or later) or no threads support
         #include "lf_POSIX_threads_support.h"
diff --git a/include/core/platform/lf_macos_support.h b/include/core/platform/lf_macos_support.h
index a769f6122..4aad2d19d 100644
--- a/include/core/platform/lf_macos_support.h
+++ b/include/core/platform/lf_macos_support.h
@@ -41,7 +41,7 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 // The underlying physical clock for MacOS
 #define _LF_CLOCK CLOCK_MONOTONIC
 
-#if defined LF_THREADED
+#if !defined LF_SINGLE_THREADED
     #if __STDC_VERSION__ < 201112L || defined (__STDC_NO_THREADS__)
         // (Not C++11 or later) or no threads support
         #include "lf_POSIX_threads_support.h"
diff --git a/include/core/platform/lf_rp2040_support.h b/include/core/platform/lf_rp2040_support.h
index b522d9e65..1b23e3a2e 100644
--- a/include/core/platform/lf_rp2040_support.h
+++ b/include/core/platform/lf_rp2040_support.h
@@ -20,8 +20,4 @@
 #define LF_TIME_BUFFER_LENGTH 80
 #define _LF_TIMEOUT 1
 
-#ifdef LF_THREADED
-#error "Threading for baremetal RP2040 not supported" 
-#endif // LF_THREADED
-
 #endif // LF_PICO_SUPPORT_H
diff --git a/include/core/platform/lf_windows_support.h b/include/core/platform/lf_windows_support.h
index ee84d0973..b32e03bfa 100644
--- a/include/core/platform/lf_windows_support.h
+++ b/include/core/platform/lf_windows_support.h
@@ -43,7 +43,7 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <stdint.h> // For fixed-width integral types
 #include <windows.h>
 
-#if defined LF_THREADED
+#if !defined LF_SINGLE_THREADED
     #if __STDC_VERSION__ < 201112L || defined (__STDC_NO_THREADS__)
         /**
          * On Windows, one could use both a mutex or
diff --git a/include/core/platform/lf_zephyr_support.h b/include/core/platform/lf_zephyr_support.h
index d1f132323..0221010dc 100644
--- a/include/core/platform/lf_zephyr_support.h
+++ b/include/core/platform/lf_zephyr_support.h
@@ -41,7 +41,7 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <zephyr/kernel.h>
 
 #define NO_TTY
-#ifdef LF_THREADED
+#if !defined(LF_SINGLE_THREADED)
 
 typedef struct k_mutex lf_mutex_t;
 typedef struct {
@@ -73,7 +73,7 @@ bool _zephyr_bool_compare_and_swap(bool *ptr, bool value, bool newval);
  */
 int  _zephyr_val_compare_and_swap(int *ptr, int value, int newval);
 
-#endif // LF_THREADED
+#endif // !LF_SINGLE_THREADED
 
 
 
diff --git a/include/core/reactor.h b/include/core/reactor.h
index e4069844a..38f090d7c 100644
--- a/include/core/reactor.h
+++ b/include/core/reactor.h
@@ -543,7 +543,7 @@ void _lf_create_environments();
 
 
 /**
- * These functions must be implemented by both threaded and unthreaded
+ * These functions must be implemented by both threaded and single-threaded
  * runtime. Should be routed to appropriate API calls in platform.h
 */
 
diff --git a/include/core/threaded/scheduler.h b/include/core/threaded/scheduler.h
index d83307d8c..ab4bec48e 100644
--- a/include/core/threaded/scheduler.h
+++ b/include/core/threaded/scheduler.h
@@ -115,7 +115,7 @@ void lf_sched_done_with_reaction(size_t worker_number, reaction_t* done_reaction
  * @param reaction The reaction to trigger at the current tag.
  * @param worker_number The ID of the worker that is making this call. 0 should be
  *  used if there is only one worker (e.g., when the program is using the
- *  unthreaded C runtime). -1 is used for an anonymous call in a context where a
+ *  single-threaded C runtime). -1 is used for an anonymous call in a context where a
  *  worker number does not make sense (e.g., the caller is not a worker thread).
  *
  */
diff --git a/include/core/trace.h b/include/core/trace.h
index 72e2d466a..357f22b11 100644
--- a/include/core/trace.h
+++ b/include/core/trace.h
@@ -348,7 +348,7 @@ void tracepoint(
  * Trace the start of a reaction execution.
  * @param env The environment in which we are executing
  * @param reaction Pointer to the reaction_t struct for the reaction.
- * @param worker The thread number of the worker thread or 0 for unthreaded execution.
+ * @param worker The thread number of the worker thread or 0 for single-threaded execution.
  */
 void tracepoint_reaction_starts(trace_t* trace, reaction_t* reaction, int worker);
 
@@ -356,7 +356,7 @@ void tracepoint_reaction_starts(trace_t* trace, reaction_t* reaction, int worker
  * Trace the end of a reaction execution.
  * @param env The environment in which we are executing
  * @param reaction Pointer to the reaction_t struct for the reaction.
- * @param worker The thread number of the worker thread or 0 for unthreaded execution.
+ * @param worker The thread number of the worker thread or 0 for single-threaded execution.
  */
 void tracepoint_reaction_ends(trace_t* trace, reaction_t* reaction, int worker);
 
@@ -397,14 +397,14 @@ void tracepoint_user_value(void* self, char* description, long long value);
 /**
  * Trace the start of a worker waiting for something to change on the reaction queue.
  * @param env The environment in which we are executing
- * @param worker The thread number of the worker thread or 0 for unthreaded execution.
+ * @param worker The thread number of the worker thread or 0 for single-threaded execution.
  */
 void tracepoint_worker_wait_starts(trace_t* trace, int worker);
 
 /**
  * Trace the end of a worker waiting for something to change on reaction queue.
  * @param env The environment in which we are executing
- * @param worker The thread number of the worker thread or 0 for unthreaded execution.
+ * @param worker The thread number of the worker thread or 0 for single-threaded execution.
  */
 void tracepoint_worker_wait_ends(trace_t* trace, int worker);
 
@@ -426,7 +426,7 @@ void tracepoint_scheduler_advancing_time_ends(trace_t* trace);
  * Trace the occurence of a deadline miss.
  * @param env The environment in which we are executing
  * @param reaction Pointer to the reaction_t struct for the reaction.
- * @param worker The thread number of the worker thread or 0 for unthreaded execution.
+ * @param worker The thread number of the worker thread or 0 for single-threaded execution.
  */
 void tracepoint_reaction_deadline_missed(trace_t* trace, reaction_t *reaction, int worker);
 
diff --git a/lingua-franca-ref.txt b/lingua-franca-ref.txt
index 1f7391f92..5fde102e7 100644
--- a/lingua-franca-ref.txt
+++ b/lingua-franca-ref.txt
@@ -1 +1 @@
-master
+single-threaded
diff --git a/util/tracing/Makefile b/util/tracing/Makefile
index 9700ac82f..b20292d00 100644
--- a/util/tracing/Makefile
+++ b/util/tracing/Makefile
@@ -8,7 +8,7 @@ CFLAGS=	-I$(REACTOR_C)/include/core/ \
 		-I$(REACTOR_C)/include/core/modal_models \
 		-I$(REACTOR_C)/include/core/platform \
 		-I$(REACTOR_C)/include/core/utils \
-		-DLF_UNTHREADED=1 \
+		-DLF_SINGLE_THREADED=1 \
 		-Wall
 DEPS=
 LIBS=-lcurl