adj. Not variable; that always has the same value in different occurrences.
adj. constant.
adj. That cannot undergo inflection, conjugation or declension.
n. Something that does not vary; a constant.
the GNU version of the Collaborative International Dictionary of English
adj. Not given to variation or change; unalterable; unchangeable; always uniform.
n. An invariable quantity; a constant.
The Century Dictionary and Cyclopedia
Not variable; constant; uniform; unchanging.
Not capable of being varied; unalterable; unchangeable.
n. In mathematics, a quantity that does not vary; a constant.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adj. not liable to or capable of change
n. a quantity that does not vary
Word Usage
"It is this that constitutes the invariable laws of motion: I say _invariable_, because they can never change, without producing confusion in the essence of things."