Docs for Issue 2819.
diff --git a/Doc/library/math.rst b/Doc/library/math.rst
index 9bccf5d..b98f164 100644
--- a/Doc/library/math.rst
+++ b/Doc/library/math.rst
@@ -103,6 +103,12 @@
Return the fractional and integer parts of *x*. Both results carry the sign of
*x*, and both are floats.
+.. function:: sum(iterable)
+
+ Return an accurate floating point sum of values in the iterable. Avoids
+ loss of precision by tracking multiple intermediate partial sums. The
+ algorithm's accuracy depends on IEEE-754 arithmetic guarantees and the
+ typical case where the rounding mode is half-even.
.. function:: trunc(x)