inverse

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Reversed in order, nature, or effect.
• adjective Mathematics Of or relating to an inverse or an inverse function.
• adjective Archaic Turned upside down; inverted.
• noun Something that is opposite, as in sequence or character; the reverse.
• noun Mathematics One of a pair of elements in a set whose result under the operation of the set is the identity element, especially.
• noun The reciprocal of a designated quantity.
• noun The negative of a designated quantity.

from The Century Dictionary.

• In logic, with conclusion as hypothesis and hypothesis as conclusion.
• noun In logic, a proposition made by simply interchanging the hypothesis and conclusion of another, without any restriction.
• noun In mathematics, an inverse point, curve, function, ratio, proportion, etc.
• noun In rouge-et-noir, the triangular space in which bets are placed when wagering that the first card dealt for a color will not be the same color as the one that wins the coup: opposed to couleur. See rouge-et-noir.
• Turned end for end, or in the opposite direction; having a contrary course or tendency; inverted: opposed to direct.
• In mathematics, opposite in nature and effect: said with reference to any two operations which, when both performed in succession upon the same quantity, leave it unaltered: thus, subtraction is inverse to addition, division to multiplication, extraction of roots to the raising of powers, etc.
• noun An inverted state or condition; a direct opposite; something directly or absolutely contrary to something else: as, the inverse of a proposition.

from the GNU version of the Collaborative International Dictionary of English.

• noun That which is inverse.
• adjective Opposite in order, relation, or effect; reversed; inverted; reciprocal; -- opposed to direct.
• adjective (Bot.) Inverted; having a position or mode of attachment the reverse of that which is usual.
• adjective (Math.) Opposite in nature and effect; -- said with reference to any two operations, which, when both are performed in succession upon any quantity, reproduce that quantity. The symbol of an inverse operation is the symbol of the direct operation with -1 as an index. Thus sin-1 x means the arc or angle whose sine is x.
• adjective (Geom.) two figures, such that each point of either figure is inverse to a corresponding point in the order figure.
• adjective (Geom.) two points lying on a line drawn from the center of a fixed circle or sphere, and so related that the product of their distances from the center of the circle or sphere is equal to the square of the radius.
• adjective (Math.) the ratio of the reciprocals of two quantities.
• adjective an equality between a direct ratio and a reciprocal ratio; thus, 4 : 2 : : 1/3 : 1/6, or 4 : 2 : : 3 : 6, inversely.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective Opposite in effect or nature or order
• adjective reverse, opposite in or order
• adjective mathematics Having the properties of an inverse.
• adjective A grammatical number marking that indicates the opposite grammatical number (or numbers) of the default number specification of noun class.
• noun The opposite of a given, due to contrary nature or effect.
• noun The reverse version of a procedure.
• noun mathematics The inverse of an element x with respect to a binary operation is an element that when combined with x yields the appropriate identity element.
• noun logic A statement constructed from the negatives of the premise and conclusion of some other statement: ~p → ~q is the inverse of p → q.
• verb surveying To compute the bearing and distance between two points.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun something inverted in sequence or character or effect
• adjective opposite in nature or effect or relation to another quantity
• adjective reversed (turned backward) in order or nature or effect