Origin: L, fr. Gr. Metathesis, fr. Metatithenai to place differently, to transpose; meta beyond, over + tithenai to place, set. See Thesis.

1. Transposition, as of the letters or syllables of a word; as, pistris for pristis; meagre for meager.

2. <medicine> A mere change in place of a morbid substance, without removal from the body.

3. <chemistry> The act, process, or result of exchange, substitution, or replacement of atoms and radicals; thus, by metathesis an acid gives up all or part of its hydrogen, takes on an equivalent amount of a metal or base, and forms a salt.

(01 Mar 1998)