in·verse 
(ĭn-vûrs, ĭnvûrs′)
(ĭn-vûrs, ĭnvûrs′)adj.
1. Reversed in order, nature, or effect.
2. Mathematics Of or relating to an inverse or an inverse function.
3. Archaic Turned upside down; inverted.
n. (ĭnvûrs′, ĭn-vûrs)
1. Something that is opposite, as in sequence or character; the reverse.
2. Mathematics One of a pair of elements in a set whose result under the operation of the set is the identity element, especially:
a. The reciprocal of a designated quantity. Also called multiplicative inverse.
b. The negative of a designated quantity. Also called additive inverse.
[Middle English, from Latin inversus, past participle of invertere, to invert; see INVERT.]
in·versely adv.