Pronunciation: (i-kwiv'u-luns or, for 3, ē"kwu-vā'luns), [key]
1. the state or fact of being equivalent; equality in value, force, significance, etc.
2. an instance of this; an equivalent.
3. Chem.the quality of having equal valence.
4. Logic, Math.
a. Also called material implication. the relation between two propositions such that the second is not false when the first is true.
b. Also called material equivalence. the relation between two propositions such that they are either both true or both false.
c. the relation between two propositions such that each logically implies the other.
(of a logical or mathematical relationship) reflexive, symmetrical, and transitive. Also,equivalency (for defs. 1, 2).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.