1. (a.) Equal in worth or value, force, power, effect; as, equivalent expressions\; alike in significance and value; of the same import or meaning.

2. (a.) Equal in measure but not admitting of superposition; -- applied to magnitudes; as, a square may be equivalent to a triangle.

3. (a.) Contemporaneous in origin; as, the equivalent strata of different countries.

4. (n.) Something equivalent; that which is equal in value, worth, weight, or force; as, to offer an equivalent for damage done.

5. (n.) That comparative quantity by weight of an element which possesses the same chemical value as other elements, as determined by actual experiment and reference to the same standard. Specifically: (a) The comparative proportions by which one element replaces another in any particular compound; thus, as zinc replaces hydrogen in hydrochloric acid, their equivalents are 32.5 and 1. (b) The combining proportion by weight of a substance, or the number expressing this proportion, in any particular compound; as, the equivalents of hydrogen and oxygen in water are respectively 1 and 8, and in hydric dioxide 1 and 16.

6. (n.) A combining unit, whether an atom, a radical, or a molecule; as, in acid salt two or more equivalents of acid unite with one or more equivalents of base.

7. (v. t.) To make the equivalent to; to equal; equivalence.

Doppelganger accordant actual thing affirmative agent agnate agreeable agreeing akin alike all one all the same ally alter ego alternate alternative analogon analogous analogue analogy answerable answering associate at one backup balance ballast brother carbon copy change changeable changeling close close copy close match coequal coexistent coexisting coextensive cognate coherent coincident coincidental coinciding commensurate commutable commutative companion comparable comparison compatible compeer complement complemental complementary concordant concurring conformable congenator congener congenial congruent congruous consentaneous consentient consideration consistent consonant convertible cooperating cooperative coordinate copy correlate correlative correspondent corresponding coterminous counterbalance counterfeit counterpart counterpoise counterweight dead ringer deputy ditto double dummy duplicate en rapport equal equalizing equiparant equipoise equipollent ersatz even exact counterpart exchange exchanged facsimile fake fellow fill-in ghost ghostwriter give-and-take harmonious homograph homologous homonym homophone idem identic identical identical same image imitation in accord in agreement in rapport in sync in synchronization inaccordance indistinguishable inharmony interchangeable interchanged kindred spirit like like-minded likeness locum tenens makeshift makeweight match matching mate metaphor metonymy mock much the same mutual near duplicate next best thing no other none other obverse of a kind of a piece of a size of like mind of one mind offset on all fours opposite number parallel paralleling peer pendant permutable personnel phony picture pinch pinch hitter positive proportionate provisional proxy quid pro quo reciprocal reciprocating reciprocative reconcilable relief replacement replica representative reserve reserves retaliatory returnable ringer rival second self second string secondary self-consistent selfsame setoff sign similar similitude simulacrum sister something of value soul mate spare spares spit and image spitting image stand-in standard stopgap sub substituent substitute substitution succedaneum such suchlike superseder supplanter surrogate swapped switched symbiotic symbol synchronized synchronous synecdoche synonym synonymous tally tantamount temporary tentative the like of the likes of the same the same difference third string tit for tat token traded transposed twin unanimous understudy undifferenced uniform unisonant unisonous utility utility player very image very same vicar vicarious vice-president vice-regent