Equal, as in value, force, or meaning. Having similar or identical effects. Being essentially equal, all things considered: a wish that was equivalent to a command. Mathematics Capable of being put into a one-to-one relationship. Used of two sets. Having virtually identical or corresponding parts. Of or relating to corresponding elements under an equivalence relation. Chemistry Having the same ability to combine. Logic Having equivalence: equivalent propositions. Something that is essentially equal to another:"The hand is not the biological equivalent of a hammer or a screwdriver; the hand is a multipurpose tool like a Swiss Army knife"(Jonathan Gottschall). Chemistry Equivalent weight.