Tangent

Noun

 * 1)  A straight line touching a curve at a single point without crossing it there.
 * 2)  The ratio of the sine to the cosine, in either the real or complex numbers.-->
 * 3) A topic nearly unrelated to the main topic, but having a point in common with it.
 * 4) A small metal blade by which a clavichord produces sound.

Derived terms

 * arctangent
 * cotangent
 * hyberbolic tangent

Related terms

 * tangential

Adjective

 * 1)  Touching a curve at a single point but not crossing it at that point.
 * 2) Of a topic, only loosely related to a main topic.

Thesaurus
abutter, adjoiner, air line, approach, asymptote, axis, beeline, borderer, bottleneck, bystander, chord, collision course, concentralization, concentration, concourse, concurrence, confluence, conflux, congress, convergence, converging, crossing, diagonal, diameter, direct line, directrix, edge, focalization, focus, funnel, great-circle course, hub, immediate neighbor, looker-on, meeting, mutual approach, narrowing gap, neighbor, neighborer, normal, onlooker, perpendicular, radius, radius vector, right line, secant, segment, shortcut, side, spokes, straight, straight course, straight line, straight stretch, straightaway, streamline, transversal, vector