Metathesis
Metathesis , noun
[Latin, from Greek meta`qesis, from metatiqe`nai to place differently, to transpose; meta` beyond, over + tiqe`nai to place, set. See Thesis.]
1.
(Grammar) 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.