- (in a right triangle) the ratio of the side adjacent to a given angle to the side opposite.
- the tangent of the complement, or the reciprocal of the tangent, of a given angle or arc. Abbreviation: cot, ctn
- (of an angle) a trigonometric function that in a right-angled triangle is the ratio of the length of the adjacent side to that of the opposite side; the reciprocal of tangent
