ch 2 - the language of first-order logic

http://en.wikipedia.org/wiki/First-order_logic#Alphabet

Abbreviations:
(a \supset b) for (not a or b)
safer to read as disjunction than as “if ... then ...”
(a three-vertical-lines b) for (((a \supset b)) or ((b \supset a)))

well-formed formulas[3] or wffs

A is a subset of B and conversely B is a superset of A
* B is a proper superset of A; this is written as B\supsetneq A.