**Tan"gent** (?), n. [L. *tangens*, *-entis*, p.pr. of *tangere* to touch; akin to Gr. having seized: cf. F. *tangente*. Cf. Attain, Contaminate, Contingent, Entire, Tact, Taste, Tax, v. t.] Geom.

A tangent line curve, or surface; specifically, that portion of the straight line tangent to a curve that is between the point of tangency and a given line, the given line being, for example, the axis of abscissas, or a radius of a circle produced. See Trigonometrical function, under Function.

Artificial, or Logarithmic, tangent, the logarithm of the natural tangent of an arc. -- Natural tangent, a decimal expressing the length of the tangent of an arc, the radius being reckoned unity. -- Tangent galvanometer Elec., a form of galvanometer having a circular coil and a short needle, in which the tangent of the angle of deflection of the needle is proportional to the strength of the current. -- Tangent of an angle, the natural tangent of the arc subtending or measuring the angle. -- Tangent of an arc, a right line, as ta, touching the arc of a circle at one extremity a, and terminated by a line ct, passing from the center through the other extremity o.
<-- references are to a figure showing the tangent of an arc -->

© Webster 1913.

**Tan"gent**, a. [L. *tangens*, *-entis*, p.pr.]

Touching; touching at a single point

; specifically

Geom. meeting a curve or surface at a point and having at that point the same direction as the curve or surface; -- said of a straight line, curve, or surface; as, a line **tangent** to a curve; a curve **tangent** to a surface; **tangent** surfaces.

Tangent plane Geom., a plane which touches a surface in a point or line. -- Tangent scale Gun., a kind of breech sight for a cannon. -- Tangent screw Mach., an endless screw; a worm.

© Webster 1913.