Here are some notes about the different HTML 4 entities. The data comes section 24 of the HTML 4 specifications: Character entity references in HTML 4.
there is no Sigmaf, and no U+03A2 character either
bullet is NOT the same as bullet operator
alef symbol is NOT the same as hebrew letter alef, U+05D0 although the same glyph could be used to depict both characters
ISO 10646 does not say that lArr is the same as the 'is implied by' arrow but also does not have any other character for that function. So ? lArr can be used for 'is implied by' as ISOtech suggests
ISO 10646 does not say this is the 'implies' character but does not have another character with this function so ? rArr can be used for 'implies' as ISOtech suggests
should there be a more memorable name than 'ni'?
prod is NOT the same character as U+03A0 'greek capital letter pi' though the same glyph might be used for both
sum is NOT the same character as U+03A3 'greek capital letter sigma' though the same glyph might be used for both
tilde operator is NOT the same character as the tilde, U+007E, although the same glyph might be used to represent both
note that nsup, 'not a superset of, U+2283' is not covered by the Symbol font encoding and is not included. Should it be, for symmetry? It is in ISOamsn
dot operator is NOT the same character as U+00B7 middle dot
lang is NOT the same character as U+003C 'less than' or U+2039 'single left-pointing angle quotation mark'
rang is NOT the same character as U+003E 'greater than' or U+203A 'single right-pointing angle quotation mark'
black here seems to mean filled as opposed to hollow
ligature is a misnomer, this is a separate character in some languages
lsaquo is proposed but not yet ISO standardized
rsaquo is proposed but not yet ISO standardized
The information in this document is Copyright © 1994-2002 W3C ® (Massachusetts Institute of Technology, Institut National de Recherche en Informatique et en Automatique, Keio University), All Rights Reserved. http://www.w3.org/Consortium/Legal/