diff --git a/src/protean/adapters/repository/elasticsearch.py b/src/protean/adapters/repository/elasticsearch.py
index d9f15a49..1d0faca9 100644
--- a/src/protean/adapters/repository/elasticsearch.py
+++ b/src/protean/adapters/repository/elasticsearch.py
@@ -47,7 +47,7 @@ class ElasticsearchModel(Document):
     def from_entity(cls, entity) -> "ElasticsearchModel":
         """Convert the entity to a Elasticsearch record"""
         item_dict = {}
-        for attribute_obj in attributes(cls.meta_.entity_cls).values():
+        for attribute_obj in attributes(cls.meta_.part_of).values():
             if isinstance(attribute_obj, Reference):
                 item_dict[attribute_obj.relation.attribute_name] = (
                     attribute_obj.relation.value
@@ -61,7 +61,7 @@ def from_entity(cls, entity) -> "ElasticsearchModel":
 
         # Elasticsearch stores identity in a special field `meta.id`.
         # Set `meta.id` to the identifier set in entity
-        id_field_name = id_field(cls.meta_.entity_cls).field_name
+        id_field_name = id_field(cls.meta_.part_of).field_name
 
         if id_field_name in item_dict:
             model_obj.meta.id = item_dict[id_field_name]
@@ -75,7 +75,7 @@ def to_entity(cls, item: "ElasticsearchModel"):
 
         # Convert the values in ES Model as a dictionary
         values = item.to_dict()
-        for field_name in attributes(cls.meta_.entity_cls):
+        for field_name in attributes(cls.meta_.part_of):
             item_dict[field_name] = values.get(field_name, None)
 
         identifier = None
@@ -90,14 +90,14 @@ def to_entity(cls, item: "ElasticsearchModel"):
 
         # Elasticsearch stores identity in a special field `meta.id`.
         # Extract identity from `meta.id` and set identifier
-        id_field_name = id_field(cls.meta_.entity_cls).field_name
+        id_field_name = id_field(cls.meta_.part_of).field_name
         item_dict[id_field_name] = identifier
 
         # Set version from document meta, only if `_version` attr is present
-        if hasattr(cls.meta_.entity_cls, "_version"):
+        if hasattr(cls.meta_.part_of, "_version"):
             item_dict["_version"] = item.meta.version
 
-        entity_obj = cls.meta_.entity_cls(item_dict)
+        entity_obj = cls.meta_.part_of(item_dict)
 
         return entity_obj
 
@@ -439,7 +439,7 @@ def construct_model_class(self, entity_cls):
             model_cls = self._model_classes[entity_cls.meta_.schema_name]
         else:
             meta_ = Options()
-            meta_.entity_cls = entity_cls
+            meta_.part_of = entity_cls
 
             # Construct Inner Index class with options
             options = {}
diff --git a/src/protean/adapters/repository/memory.py b/src/protean/adapters/repository/memory.py
index 7736a63d..ae4290be 100644
--- a/src/protean/adapters/repository/memory.py
+++ b/src/protean/adapters/repository/memory.py
@@ -26,7 +26,7 @@ def derive_schema_name(model_cls):
     if hasattr(model_cls.meta_, "schema_name"):
         return model_cls.meta_.schema_name
     else:
-        return model_cls.meta_.entity_cls.meta_.schema_name
+        return model_cls.meta_.part_of.meta_.schema_name
 
 
 class MemoryModel(BaseModel):
@@ -43,7 +43,7 @@ def from_entity(cls, entity) -> "MemoryModel":
     @classmethod
     def to_entity(cls, item: "MemoryModel"):
         """Convert the dictionary record to an entity"""
-        return cls.meta_.entity_cls(**item)
+        return cls.meta_.part_of(**item)
 
 
 class MemorySession:
@@ -148,7 +148,7 @@ def decorate_model_class(self, entity_cls, model_cls):
             }
 
             meta_ = Options()
-            meta_.entity_cls = entity_cls
+            meta_.part_of = entity_cls
 
             custom_attrs.update({"meta_": meta_})
             # FIXME Ensure the custom model attributes are constructed properly
@@ -170,7 +170,7 @@ def construct_model_class(self, entity_cls):
             model_cls = self._model_classes[entity_cls.meta_.schema_name]
         else:
             meta_ = Options()
-            meta_.entity_cls = entity_cls
+            meta_.part_of = entity_cls
 
             attrs = {
                 "meta_": meta_,
diff --git a/src/protean/adapters/repository/sqlalchemy.py b/src/protean/adapters/repository/sqlalchemy.py
index 9c9afe17..7c42bd9d 100644
--- a/src/protean/adapters/repository/sqlalchemy.py
+++ b/src/protean/adapters/repository/sqlalchemy.py
@@ -133,7 +133,7 @@ def derive_schema_name(model_cls):
     ):
         return model_cls.meta_.schema_name
     else:
-        return model_cls.meta_.entity_cls.meta_.schema_name
+        return model_cls.meta_.part_of.meta_.schema_name
 
 
 class SqlalchemyModel(orm.DeclarativeBase, BaseModel):
@@ -169,7 +169,7 @@ def field_mapping_for(field_obj: Field):
 
         # Update the class attrs with the entity attributes
         if "meta_" in subclass.__dict__:
-            entity_cls = subclass.__dict__["meta_"].entity_cls
+            entity_cls = subclass.__dict__["meta_"].part_of
             for _, field_obj in attributes(entity_cls).items():
                 attribute_name = field_obj.attribute_name
 
@@ -243,7 +243,7 @@ def __tablename__(cls):
     def from_entity(cls, entity):
         """Convert the entity to a model object"""
         item_dict = {}
-        for attribute_obj in attributes(cls.meta_.entity_cls).values():
+        for attribute_obj in attributes(cls.meta_.part_of).values():
             if isinstance(attribute_obj, Reference):
                 item_dict[attribute_obj.relation.attribute_name] = (
                     attribute_obj.relation.value
@@ -258,9 +258,9 @@ def from_entity(cls, entity):
     def to_entity(cls, model_obj: "SqlalchemyModel"):
         """Convert the model object to an entity"""
         item_dict = {}
-        for field_name in attributes(cls.meta_.entity_cls):
+        for field_name in attributes(cls.meta_.part_of):
             item_dict[field_name] = getattr(model_obj, field_name, None)
-        return cls.meta_.entity_cls(item_dict)
+        return cls.meta_.part_of(item_dict)
 
 
 class SADAO(BaseDAO):
@@ -683,7 +683,7 @@ def decorate_model_class(self, entity_cls, model_cls):
             custom_attrs = {**custom_attrs, **columns}
 
             meta_ = Options(model_cls.meta_)
-            meta_.entity_cls = entity_cls
+            meta_.part_of = entity_cls
             meta_.schema_name = (
                 schema_name if meta_.schema_name is None else meta_.schema_name
             )
@@ -711,7 +711,7 @@ def construct_model_class(self, entity_cls):
         else:
             # Construct a new Meta object with existing values
             meta_ = Options()
-            meta_.entity_cls = entity_cls
+            meta_.part_of = entity_cls
             # If schema_name is not provided, sqlalchemy can throw
             #   sqlalchemy.exc.InvalidRequestError: Class does not
             #   have a __table__ or __tablename__ specified and
diff --git a/src/protean/core/model.py b/src/protean/core/model.py
index 3fcbb7f3..eee21774 100644
--- a/src/protean/core/model.py
+++ b/src/protean/core/model.py
@@ -21,7 +21,7 @@ def __new__(cls, *args, **kwargs):
     def _default_options(cls):
         return [
             ("database", None),
-            ("entity_cls", None),
+            ("part_of", None),
             ("schema_name", None),
         ]
 
@@ -39,7 +39,7 @@ def to_entity(cls, *args, **kwargs):
 def model_factory(element_cls, **kwargs):
     element_cls = derive_element_class(element_cls, BaseModel, **kwargs)
 
-    if not element_cls.meta_.entity_cls:
+    if not element_cls.meta_.part_of:
         raise IncorrectUsageError(
             {
                 "_entity": [
diff --git a/src/protean/domain/__init__.py b/src/protean/domain/__init__.py
index 25b0a4ec..2a1b8331 100644
--- a/src/protean/domain/__init__.py
+++ b/src/protean/domain/__init__.py
@@ -447,7 +447,7 @@ def _register_element(self, element_type, element_cls, **kwargs):  # noqa: C901
 
         if element_type == DomainObjects.MODEL:
             # Remember model association with aggregate/entity class, for easy fetching
-            self._models[fqn(new_cls.meta_.entity_cls)] = new_cls
+            self._models[fqn(new_cls.meta_.part_of)] = new_cls
 
         # Register element with domain
         self._domain_registry.register_element(new_cls)
diff --git a/tests/adapters/model/dict_model/tests.py b/tests/adapters/model/dict_model/tests.py
index ae4d5de0..5a906428 100644
--- a/tests/adapters/model/dict_model/tests.py
+++ b/tests/adapters/model/dict_model/tests.py
@@ -85,7 +85,7 @@ class TestCustomModel:
     def test_that_custom_model_is_associated_with_entity(self, test_domain):
         test_domain.register(Provider)
         test_domain.register(
-            ProviderCustomModel, entity_cls=Provider, schema_name="adults"
+            ProviderCustomModel, part_of=Provider, schema_name="adults"
         )
 
         assert (
@@ -98,7 +98,7 @@ def test_that_model_can_be_registered_with_domain_annotation(self, test_domain):
 
         test_domain.register(Receiver)
 
-        @test_domain.model(entity_cls=Receiver)
+        @test_domain.model(part_of=Receiver)
         class ReceiverInlineModel:
             about = Text()
 
diff --git a/tests/adapters/model/elasticsearch_model/conftest.py b/tests/adapters/model/elasticsearch_model/conftest.py
index 7c0b4a91..9369c193 100644
--- a/tests/adapters/model/elasticsearch_model/conftest.py
+++ b/tests/adapters/model/elasticsearch_model/conftest.py
@@ -31,7 +31,7 @@ def setup_db():
         domain.register(ComplexUser)
         domain.register(Provider)
         domain.register_model(
-            ProviderCustomModel, entity_cls=Provider, schema_name="providers"
+            ProviderCustomModel, part_of=Provider, schema_name="providers"
         )
         domain.init(traverse=False)
 
diff --git a/tests/adapters/model/elasticsearch_model/tests.py b/tests/adapters/model/elasticsearch_model/tests.py
index ca5df047..c2f37641 100644
--- a/tests/adapters/model/elasticsearch_model/tests.py
+++ b/tests/adapters/model/elasticsearch_model/tests.py
@@ -113,7 +113,7 @@ class Index:
                     name = "people"
 
             test_domain.register(Person)
-            test_domain.register_model(PeopleModel, entity_cls=Person)
+            test_domain.register_model(PeopleModel, part_of=Person)
 
             model_cls = test_domain.repository_for(Person)._model
             assert model_cls.__name__ == "PeopleModel"
@@ -173,7 +173,7 @@ class Index:
                     name = "custom-people"
 
             test_domain.register(Person)
-            test_domain.register_model(PeopleModel, entity_cls=Person)
+            test_domain.register_model(PeopleModel, part_of=Person)
 
             model_cls = test_domain.repository_for(Person)._model
             assert model_cls.__name__ == "PeopleModel"
@@ -210,7 +210,7 @@ class Index:
                     settings = {"number_of_shards": 2}
 
             test_domain.register(Person)
-            test_domain.register_model(PeopleModel, entity_cls=Person)
+            test_domain.register_model(PeopleModel, part_of=Person)
 
             model_cls = test_domain.repository_for(Person)._model
             assert model_cls.__name__ == "PeopleModel"
@@ -269,7 +269,7 @@ class TestCustomModel:
     def test_that_custom_model_can_be_associated_with_entity(self, test_domain):
         test_domain.register(Provider)
         test_domain.register_model(
-            ProviderCustomModel, entity_cls=Provider, schema_name="providers"
+            ProviderCustomModel, part_of=Provider, schema_name="providers"
         )
 
         model_cls = test_domain.repository_for(Provider)._model
@@ -280,7 +280,7 @@ def test_that_explicit_schema_name_takes_precedence_over_generated(
     ):
         test_domain.register(Provider)
         test_domain.register_model(
-            ProviderCustomModel, entity_cls=Provider, schema_name="providers"
+            ProviderCustomModel, part_of=Provider, schema_name="providers"
         )
 
         # FIXME Should schema name be equated to the overridden name in the model?
@@ -293,7 +293,7 @@ def test_that_explicit_schema_name_takes_precedence_over_generated(
     def test_that_custom_model_is_persisted_via_dao(self, test_domain):
         test_domain.register(Provider)
         test_domain.register_model(
-            ProviderCustomModel, entity_cls=Provider, schema_name="providers"
+            ProviderCustomModel, part_of=Provider, schema_name="providers"
         )
 
         provider_dao = test_domain.repository_for(Provider)._dao
@@ -303,7 +303,7 @@ def test_that_custom_model_is_persisted_via_dao(self, test_domain):
     def test_that_custom_model_is_retrievable_via_dao(self, test_domain):
         test_domain.register(Provider)
         test_domain.register_model(
-            ProviderCustomModel, entity_cls=Provider, schema_name="providers"
+            ProviderCustomModel, part_of=Provider, schema_name="providers"
         )
 
         provider_dao = test_domain.repository_for(Provider)._dao
@@ -318,7 +318,7 @@ def test_that_model_can_be_registered_with_domain_annotation(self, test_domain):
 
         test_domain.register(Receiver)
 
-        @test_domain.model(entity_cls=Receiver)
+        @test_domain.model(part_of=Receiver)
         class ReceiverInlineModel:
             name = Text(fields={"raw": Keyword()})
 
@@ -343,7 +343,7 @@ def test_persistence_via_model_registered_with_domain_annotation(self, test_doma
 
         test_domain.register(Receiver)
 
-        @test_domain.model(entity_cls=Receiver)
+        @test_domain.model(part_of=Receiver)
         class ReceiverInlineModel:
             id = Keyword()
             name = Text(fields={"raw": Keyword()})
diff --git a/tests/adapters/model/sqlalchemy_model/postgresql/conftest.py b/tests/adapters/model/sqlalchemy_model/postgresql/conftest.py
index 1357b2ea..dcffcd1c 100644
--- a/tests/adapters/model/sqlalchemy_model/postgresql/conftest.py
+++ b/tests/adapters/model/sqlalchemy_model/postgresql/conftest.py
@@ -41,7 +41,7 @@ def setup_db():
         domain.register(IntegerListUser)
 
         domain.register_model(
-            ProviderCustomModel, entity_cls=Provider, schema_name="adults"
+            ProviderCustomModel, part_of=Provider, schema_name="adults"
         )
         domain.init(traverse=False)
 
diff --git a/tests/adapters/model/sqlalchemy_model/postgresql/test_model.py b/tests/adapters/model/sqlalchemy_model/postgresql/test_model.py
index ce444908..1bee84e2 100644
--- a/tests/adapters/model/sqlalchemy_model/postgresql/test_model.py
+++ b/tests/adapters/model/sqlalchemy_model/postgresql/test_model.py
@@ -100,7 +100,7 @@ def test_conversation_from_model_to_entity(self, test_domain):
 class TestCustomModel:
     def test_that_custom_model_can_be_associated_with_entity(self, test_domain):
         test_domain.register(
-            ProviderCustomModel, entity_cls=Provider, schema_name="adults"
+            ProviderCustomModel, part_of=Provider, schema_name="adults"
         )
         model_cls = test_domain.repository_for(Provider)._model
         assert model_cls.__name__ == "ProviderCustomModel"
@@ -110,7 +110,7 @@ def test_that_model_can_be_registered_with_domain_annotation(self, test_domain):
 
         test_domain.register(Receiver)
 
-        @test_domain.model(entity_cls=Receiver)
+        @test_domain.model(part_of=Receiver)
         class ReceiverInlineModel:
             name = Column(Text)
 
diff --git a/tests/adapters/model/sqlalchemy_model/sqlite/conftest.py b/tests/adapters/model/sqlalchemy_model/sqlite/conftest.py
index 1912412f..a9890eea 100644
--- a/tests/adapters/model/sqlalchemy_model/sqlite/conftest.py
+++ b/tests/adapters/model/sqlalchemy_model/sqlite/conftest.py
@@ -28,7 +28,7 @@ def setup_db():
         domain.register(Provider)
         domain.register(User)
         domain.register_model(
-            ProviderCustomModel, entity_cls=Provider, schema_name="adults"
+            ProviderCustomModel, part_of=Provider, schema_name="adults"
         )
         domain.init(traverse=False)
 
diff --git a/tests/adapters/model/sqlalchemy_model/sqlite/test_model.py b/tests/adapters/model/sqlalchemy_model/sqlite/test_model.py
index 21e81104..168a5a77 100644
--- a/tests/adapters/model/sqlalchemy_model/sqlite/test_model.py
+++ b/tests/adapters/model/sqlalchemy_model/sqlite/test_model.py
@@ -100,7 +100,7 @@ def test_conversation_from_model_to_entity(self, test_domain):
 class TestCustomModel:
     def test_that_custom_model_can_be_associated_with_entity(self, test_domain):
         test_domain.register(
-            ProviderCustomModel, entity_cls=Provider, schema_name="adults"
+            ProviderCustomModel, part_of=Provider, schema_name="adults"
         )
         model_cls = test_domain.repository_for(Provider)._model
         assert model_cls.__name__ == "ProviderCustomModel"
@@ -110,7 +110,7 @@ def test_that_model_can_be_registered_with_domain_annotation(self, test_domain):
 
         test_domain.register(Receiver)
 
-        @test_domain.model(entity_cls=Receiver)
+        @test_domain.model(part_of=Receiver)
         class ReceiverInlineModel:
             name = Column(Text)