in mathematics, the trigonometric function that, for an acute angle in a right-angled triangle, is the ratio between the shorter sides opposite and adjacent to the angle: compare sine, cosine
a straight line touching a curve or surface at only one point
an upright flat-ended metal pin at the inner end of a clavichord key that strikes the string to produce the note
fly/go off at a tangent/fly/go off at/on a tangent
to change suddenly from one subject or, course of action, etc, to another
[medieval Latin tangent-, tangens, from linea tangens tangent line, from tangere to touch]