diff --git a/docs/site/BelongsTo-relation.md b/docs/site/BelongsTo-relation.md
index 42d32706948a..3a075bba0fdf 100644
--- a/docs/site/BelongsTo-relation.md
+++ b/docs/site/BelongsTo-relation.md
@@ -130,7 +130,7 @@ export class OrderRepository extends DefaultCrudRepository<
   ) {
     super(Order, db);
     this.customer = this._createBelongsToAccessorFor(
-      'customerId',
+      'customer',
       customerRepositoryGetter,
     );
   }
diff --git a/examples/todo-list/src/repositories/todo.repository.ts b/examples/todo-list/src/repositories/todo.repository.ts
index 9eb7e1125d37..3c09cd83ff71 100644
--- a/examples/todo-list/src/repositories/todo.repository.ts
+++ b/examples/todo-list/src/repositories/todo.repository.ts
@@ -30,7 +30,7 @@ export class TodoRepository extends DefaultCrudRepository<
     super(Todo, dataSource);
 
     this.todoList = this._createBelongsToAccessorFor(
-      'todoListId',
+      'todoList',
       todoListRepositoryGetter,
     );
   }
diff --git a/packages/repository/src/decorators/model.decorator.ts b/packages/repository/src/decorators/model.decorator.ts
index 0caeb1404823..4c3934e8d981 100644
--- a/packages/repository/src/decorators/model.decorator.ts
+++ b/packages/repository/src/decorators/model.decorator.ts
@@ -55,35 +55,46 @@ export function model(definition?: Partial<ModelDefinitionSyntax>) {
     decorator(target);
 
     // Build "ModelDefinition" and store it on model constructor
-    const modelDef = new ModelDefinition(def);
-
-    const propertyMap: PropertyMap =
-      MetadataInspector.getAllPropertyMetadata(
-        MODEL_PROPERTIES_KEY,
-        target.prototype,
-      ) || {};
+    buildModelDefinition(target, def);
+  };
+}
 
-    for (const p in propertyMap) {
-      const propertyDef = propertyMap[p];
-      const designType = MetadataInspector.getDesignTypeForProperty(
-        target.prototype,
-        p,
-      );
-      if (!propertyDef.type) {
-        propertyDef.type = designType;
-      }
-      modelDef.addProperty(p, propertyDef);
+/**
+ * Build model definition from decorations
+ * @param target Target model class
+ * @param def Model definition spec
+ */
+export function buildModelDefinition(
+  target: Function & {definition?: ModelDefinition | undefined},
+  def?: ModelDefinitionSyntax,
+) {
+  // Check if the definition for this class has been built
+  if (!def && target.definition && target.definition.name === target.name) {
+    return target.definition;
+  }
+  const modelDef = new ModelDefinition(def || {name: target.name});
+  const prototype = target.prototype;
+  const propertyMap: PropertyMap =
+    MetadataInspector.getAllPropertyMetadata(MODEL_PROPERTIES_KEY, prototype) ||
+    {};
+  for (const p in propertyMap) {
+    const propertyDef = propertyMap[p];
+    const designType = MetadataInspector.getDesignTypeForProperty(prototype, p);
+    if (!propertyDef.type) {
+      propertyDef.type = designType;
     }
-
-    target.definition = modelDef;
-
-    const relationMap: RelationDefinitionMap =
-      MetadataInspector.getAllPropertyMetadata(
-        RELATIONS_KEY,
-        target.prototype,
-      ) || {};
-    target.definition.relations = relationMap;
-  };
+    modelDef.addProperty(p, propertyDef);
+  }
+  target.definition = modelDef;
+  const relationMeta: RelationDefinitionMap =
+    MetadataInspector.getAllPropertyMetadata(RELATIONS_KEY, prototype) || {};
+  const relations: RelationDefinitionMap = {};
+  // Build an object keyed by relation names
+  Object.values(relationMeta).forEach(r => {
+    relations[r.name] = r;
+  });
+  target.definition.relations = relations;
+  return modelDef;
 }
 
 /**
diff --git a/packages/repository/src/relations/belongs-to/belongs-to.decorator.ts b/packages/repository/src/relations/belongs-to/belongs-to.decorator.ts
index dadffdf6efae..c48b57e193bf 100644
--- a/packages/repository/src/relations/belongs-to/belongs-to.decorator.ts
+++ b/packages/repository/src/relations/belongs-to/belongs-to.decorator.ts
@@ -39,13 +39,13 @@ export function belongsTo<T extends Entity>(
       // default values, can be customized by the caller
       {
         keyFrom: decoratedKey,
+        name: relationName,
       },
       // properties provided by the caller
       definition,
       // properties enforced by the decorator
       {
         type: RelationType.belongsTo,
-        name: relationName,
         source: decoratedTarget.constructor,
         target: targetResolver,
       },
diff --git a/packages/repository/src/relations/has-many/has-many.decorator.ts b/packages/repository/src/relations/has-many/has-many.decorator.ts
index 5019ce6769a7..1fc3f26d5a0a 100644
--- a/packages/repository/src/relations/has-many/has-many.decorator.ts
+++ b/packages/repository/src/relations/has-many/has-many.decorator.ts
@@ -25,13 +25,12 @@ export function hasMany<T extends Entity>(
 
     const meta: HasManyDefinition = Object.assign(
       // default values, can be customized by the caller
-      {},
+      {name: key},
       // properties provided by the caller
       definition,
       // properties enforced by the decorator
       {
         type: RelationType.hasMany,
-        name: key,
         source: decoratedTarget.constructor,
         target: targetResolver,
       },
diff --git a/packages/repository/src/relations/relation.decorator.ts b/packages/repository/src/relations/relation.decorator.ts
index e30346587920..72a09d7f0c56 100644
--- a/packages/repository/src/relations/relation.decorator.ts
+++ b/packages/repository/src/relations/relation.decorator.ts
@@ -6,6 +6,7 @@
 import {PropertyDecoratorFactory} from '@loopback/context';
 import {Model, RelationDefinitionMap} from '../model';
 import {RelationType} from './relation.types';
+import {buildModelDefinition} from '../decorators';
 
 export const RELATIONS_KEY = 'loopback:relations';
 
@@ -28,7 +29,9 @@ export function relation(definition?: Object) {
 export function getModelRelations(
   modelCtor: typeof Model,
 ): RelationDefinitionMap {
-  return (modelCtor.definition && modelCtor.definition.relations) || {};
+  // Build model definitions if `@model` is missing
+  const modelDef = buildModelDefinition(modelCtor);
+  return (modelDef && modelDef.relations) || {};
 }
 
 //
diff --git a/packages/repository/test/fixtures/repositories/order.repository.ts b/packages/repository/test/fixtures/repositories/order.repository.ts
index 6a21c755c9f2..b8e9e2bd8fc2 100644
--- a/packages/repository/test/fixtures/repositories/order.repository.ts
+++ b/packages/repository/test/fixtures/repositories/order.repository.ts
@@ -29,7 +29,7 @@ export class OrderRepository extends DefaultCrudRepository<
   ) {
     super(Order, db);
     this.customer = this._createBelongsToAccessorFor(
-      'customerId',
+      'customer',
       customerRepositoryGetter,
     );
   }
diff --git a/packages/repository/test/unit/decorator/relation.decorator.unit.ts b/packages/repository/test/unit/decorator/relation.decorator.unit.ts
index cee01aba0dc4..e30f19e5fd2d 100644
--- a/packages/repository/test/unit/decorator/relation.decorator.unit.ts
+++ b/packages/repository/test/unit/decorator/relation.decorator.unit.ts
@@ -29,6 +29,7 @@ describe('relation decorator', () => {
         addressBookId: number;
       }
 
+      @model()
       class AddressBook extends Entity {
         id: number;
 
@@ -57,6 +58,15 @@ describe('relation decorator', () => {
         type: Array,
         itemType: () => Address,
       });
+
+      expect(AddressBook.definition.relations).to.eql({
+        addresses: {
+          type: RelationType.hasMany,
+          name: 'addresses',
+          source: AddressBook,
+          target: () => Address,
+        },
+      });
     });
 
     it('takes in both complex property type and hasMany metadata', () => {
@@ -126,6 +136,7 @@ describe('relation decorator', () => {
         @property({id: true})
         id: number;
       }
+      @model()
       class Address extends Entity {
         @belongsTo(() => AddressBook)
         addressBookId: number;
@@ -139,6 +150,13 @@ describe('relation decorator', () => {
           type: Number,
         },
       });
+      expect(Address.definition.relations).to.containDeep({
+        addressBook: {
+          keyFrom: 'addressBookId',
+          name: 'addressBook',
+          type: 'belongsTo',
+        },
+      });
     });
 
     it('assigns it to target key', () => {
@@ -170,6 +188,7 @@ describe('relation decorator', () => {
     });
 
     it('accepts explicit keyFrom and keyTo', () => {
+      @model()
       class Address extends Entity {
         addressId: number;
         street: string;
@@ -177,6 +196,7 @@ describe('relation decorator', () => {
         @belongsTo(() => AddressBook, {
           keyFrom: 'aForeignKey',
           keyTo: 'aPrimaryKey',
+          name: 'address-book',
         })
         addressBookId: number;
       }
@@ -194,6 +214,13 @@ describe('relation decorator', () => {
         keyFrom: 'aForeignKey',
         keyTo: 'aPrimaryKey',
       });
+      expect(Address.definition.relations).to.containDeep({
+        'address-book': {
+          type: 'belongsTo',
+          keyFrom: 'aForeignKey',
+          keyTo: 'aPrimaryKey',
+        },
+      });
     });
   });
 });