CONTRAPOSITION
Etymology
Noun
contraposition (countable and uncountable, plural contrapositions)
(countable, logic) The statement of the form "if not Q then not P", given the statement "if P then Q".
Opposition; contrast.
Source: Wiktionary
Con"tra*po*si"tion, n. Etym: [Pref. contra- + position: cf. f.
conterposition.]
1. A placing over against; opposite position. [Obs.] F. Potter.
2. (Logic)
Definition: A so-called immediate inference which consists in denying the
original subject of the contradictory predicate; e.g.: Every S is P;
therefore, no Not-P is S.
Source: Webster’s Unabridged Dictionary 1913 Edition