adjective

1. that touches; touching
2. Geom. touching and not intersecting a curve or curved surface at one and only one point: said of a line or plane

Etymology: L tangens, prp. of tangere, to touch: see tact

noun

1. Geom.
   1. a tangent line, curve, or surface
   2. the length of a straight line tangent to a curve, measured from the point of tangency to the intersection of the tangent line with the x-axis
2. Trigonometry the reciprocal of the cotangent; specif.,
   1. the ratio of the opposite side of a given acute angle in a right triangle to the adjacent side
   2. an equivalent, positive or negative ratio for certain related angles (Ex.: the tangent of 57° or 237° is 1.5399, of 123° or 303° is -1.5399) or real numbers representing radians (Ex.: the tangent of .9948 radians (57°) is 1.5399)

Etymology: < ModL (linea) tangens, tangent (line)