Clarify definition of native and implicit namespace packages

source/glossary.rst

@@ -119,6 +119,20 @@ Glossary
         extensions.
 
 
+    Implicit Namespace Package
+    Native Namespace Package
+
+        "Native namespace packages" and "implicit namespace packages" are two names for
+        the same type of namespace package. It's defined in :pep:`420`, and is available
+        in Python 3.3 and later.
+
+        The term "native" derives from the built-in feature of Python to create packages
+        without installing an extra package, such as setuptools, from outside the standard
+        library. The term "implicit" derives from the fact that you don't have to explicitly
+        declare the namespace package in a :file:`__init__.py` file.
+
+        This guide uses these names interchangeably.
+
     Import Package
 
         A Python module which can contain other modules or recursively, other

source/guides/packaging-namespace-packages.rst

@@ -71,6 +71,12 @@ from which the latter is discouraged:
 #. Use `legacy namespace packages`_. This comprises `pkgutil-style namespace packages`_
    and `pkg_resources-style namespace packages`_.
 
+.. note::
+
+    :term:`Native namespace <Native Namespace Package>` and
+    :term:`implicit namespace <Implicit Namespace Package>` packages are two
+    names for the same thing. This guide uses these names interchangeably.
+
 Native namespace packages
 -------------------------