 Definition:  
\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.
\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.
