<logic> A symbol whose referent varies or is unknown. A place-holder, as opposed to an abbreviation or name (a constant). See bound variables, constant, free variables
Individual variable of a system
Only individual variables and constants can serve as the arguments of functions and first order predicates. See domain
A variable in the metalanguage of some system S which ranges over wffs of S.
A variable ranging over attributes and relations in higher order logic.
[Glossary of First-Order Logic]
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