From the nomencl docs:
Personally, I like to specify the noprefix option and use the
optional argument to get exactly the sort order I want.
See also section 5.1 (Subgroups) about distinct groups of entries
(e.g. Greek variables, Roman variables, words).
\usepackage{makeidx} % Indexing
\makeindex
-\usepackage[intoc]{nomencl} % Abbreviation indexing
+\usepackage[intoc,noprefix]{nomencl} % Abbreviation indexing
+% Prefixes:
+% o : Operators and function symbols
+% sg : Greek symbols
+% so : Other (non-Greek/Roman symbols)
+% sr : Roman symbols
+% text : Abbreviations, chemical names, phrases, etc
\makenomenclature
\makeatletter
% override nomencl's thenomenclature to use drexel-thesis's listed@schapter