add ABC to the glossary
diff --git a/Doc/glossary.rst b/Doc/glossary.rst
index 0da14d8..693e4a7 100644
--- a/Doc/glossary.rst
+++ b/Doc/glossary.rst
@@ -24,6 +24,14 @@
2to3 is available in the standard library as :mod:`lib2to3`; a standalone
entry point is provided as :file:`Tools/scripts/2to3`.
+ Abstract Base Class
+ Abstract Base Classes (abbreviated ABCs) complement :term:`duck-typing` by
+ providing a way to define interfaces when other techniques like :func:`hasattr`
+ would be clumsy. Python comes with many builtin ABCs for data structures
+ (in the :mod:`collections` module), numbers (in the :mod:`numbers`
+ module), and streams (in the :mod:`io` module). You can create your own
+ ABC with the :mod:`abc` module.
+
argument
A value passed to a function or method, assigned to a name local to
the body. A function or method may have both positional arguments and
@@ -116,15 +124,16 @@
be any object with a :meth:`__hash__` function, not just integers starting
from zero. Called a hash in Perl.
- duck-typing
+ duck-typing
Pythonic programming style that determines an object's type by inspection
of its method or attribute signature rather than by explicit relationship
to some type object ("If it looks like a duck and quacks like a duck, it
must be a duck.") By emphasizing interfaces rather than specific types,
well-designed code improves its flexibility by allowing polymorphic
substitution. Duck-typing avoids tests using :func:`type` or
- :func:`isinstance`. Instead, it typically employs :func:`hasattr` tests or
- :term:`EAFP` programming.
+ :func:`isinstance`. (Note, however, that duck-typing can be complemented
+ with abstract base classes.) Instead, it typically employs :func:`hasattr`
+ tests or :term:`EAFP` programming.
EAFP
Easier to ask for forgiveness than permission. This common Python coding
diff --git a/Doc/library/abc.rst b/Doc/library/abc.rst
index 5eee7cc..9cdb5b3 100644
--- a/Doc/library/abc.rst
+++ b/Doc/library/abc.rst
@@ -9,10 +9,10 @@
.. versionadded:: 2.6
-This module provides the infrastructure for defining abstract base classes
-(ABCs) in Python, as outlined in :pep:`3119`; see the PEP for why this was added
-to Python. (See also :pep:`3141` and the :mod:`numbers` module regarding a type
-hierarchy for numbers based on ABCs.)
+This module provides the infrastructure for defining :term:`abstract base
+classes` (ABCs) in Python, as outlined in :pep:`3119`; see the PEP for why this
+was added to Python. (See also :pep:`3141` and the :mod:`numbers` module
+regarding a type hierarchy for numbers based on ABCs.)
The :mod:`collections` module has some concrete classes that derive from
ABCs; these can, of course, be further derived. In addition the