Roget's 21st Century Thesaurus, Third Edition Copyright © 2013 by the Philip Lief Group.

WORD ORIGIN

early 15c., from Old French invariable (14c.) and directly from Medieval Latin invariabilis, from in- "not, opposite of" (see in- (1)) + variabilis (see variable). Related: Invariably.

Roget's 21st Century Thesaurus, Third Edition Copyright © 2013 by the Philip Lief Group.