[ih-kwiv-uh-luh ns or for 3, ee-kwuh-vey-luh ns]
noun Also equivalency (for defs 1, 2).
  1. the state or fact of being equivalent; equality in value, force, significance, etc.
  2. an instance of this; an equivalent.
  3. Chemistry. the quality of having equal valence.
  4. Logic, Mathematics.
    1. Also called material implication.the relation between two propositions such that the second is not false when the first is true.
    2. Also called material equivalence.the relation between two propositions such that they are either both true or both false.
    3. the relation between two propositions such that each logically implies the other.
  1. (of a logical or mathematical relationship) reflexive, symmetrical, and transitive.

Origin of equivalence

1535–45; < Middle French < Medieval Latin aequivalentia, equivalent to Latin aequivalent- equivalent + -ia -ia; see -ence
Related formsnon·e·quiv·a·lence, noun
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for nonequivalence


  1. the relationship of being unequal or incomparable
  2. logic
    1. the relation between two statements only one of which can be true in any circumstances
    2. a function of two statements that takes the value true only when one but not both of its arguments is true
    3. a compound statement asserting that just one of its components is true
Abbreviation: exclusive or



  1. the state of being equivalent or interchangeable
  2. maths logic
    1. the relationship between two statements, each of which implies the other
    2. Also called: biconditionalthe binary truth-function that takes the value true when both component sentences are true or when both are false, corresponding to English if and only if . Symbol: ≡ or ↔, as in –(pq) ≡ – p ∨ – q
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for nonequivalence



1540s, from French équivalence, from Medieval Latin aequivalentia, from aequivalentem (see equivalent). Related: Equivalency (1530s).

Online Etymology Dictionary, © 2010 Douglas Harper