Logic Symbols

Here's a table of suggested plain-text approximations of symbols and their HTML entity references.

Symbol name		Symbol		Plain Text		HTML entity
and		∧		&		∧
or		∨		|		∨
not		¬		~		¬
conditional		→		->		→
biconditional		↔		<-> or iff		&harr;
for all		∀		A		&forall;
there exists		∃		E		&exist;
equal		=		=		=
non equal		≠		!=		&ne;
less than or equal		≤		<=		&le;
greater than or equal		≥		>=		&ge;
element of		∈		in		&isin;
not element of		∉		not in		&notin;
subset of		⊆		c		&sube;
union		∪		u		&cup;
intersection		∩		n		&cap;
powerset		℘		Pow		&weierp;
infinity		∞		infinity		&infin;

To get Greek letters, put the name of the greek letter between '&' and ';'. For example, 'Γ' produces 'Γ', and 'γ' produces 'γ'.
To indicate subscripts and superscripts use underscore _ and caret ^ (e.g., 'x_3' and 'x^3'). If you need to disambiguate from power (which is not common in logics, use ** for that instead of ^.