Fix some spelling errors in documentation and code comments
diff --git a/Lib/html/entities.py b/Lib/html/entities.py
index f7deae6..be3f627 100644
--- a/Lib/html/entities.py
+++ b/Lib/html/entities.py
@@ -221,7 +221,7 @@
     'spades':   0x2660, # black spade suit, U+2660 ISOpub
     'sub':      0x2282, # subset of, U+2282 ISOtech
     'sube':     0x2286, # subset of or equal to, U+2286 ISOtech
-    'sum':      0x2211, # n-ary sumation, U+2211 ISOamsb
+    'sum':      0x2211, # n-ary summation, U+2211 ISOamsb
     'sup':      0x2283, # superset of, U+2283 ISOtech
     'sup1':     0x00b9, # superscript one = superscript digit one, U+00B9 ISOnum
     'sup2':     0x00b2, # superscript two = superscript digit two = squared, U+00B2 ISOnum