Issue 7447: Improve docs for sum().
diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index 3b18c9a..ef913bf 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -1227,10 +1227,13 @@
Sums *start* and the items of an *iterable* from left to right and returns the
total. *start* defaults to ``0``. The *iterable*'s items are normally numbers,
- and are not allowed to be strings. The fast, correct way to concatenate a
- sequence of strings is by calling ``''.join(sequence)``. Note that
- ``sum(range(n), m)`` is equivalent to ``reduce(operator.add, range(n), m)``
- To add floating point values with extended precision, see :func:`math.fsum`\.
+ and the start value is not allowed to be a string.
+
+ For some use cases, there a good alternatives to :func:`sum`.
+ The preferred, fast way to concatenate a sequence of strings is by calling
+ ``''.join(sequence)``. To add floating point values with extended precision,
+ see :func:`math.fsum`\. To concatenate a series of iterables, consider using
+ :func:`itertools.chain`.
.. versionadded:: 2.3