Touching.

接触的。

Meeting a line or surface only at one point, but not cutting it.

【数】(几何)相切的。

Diverging from an original purpose or course; erratic.

离题的；与目的无关的。

A tangent line or surface.

【数】切线；切面。

Any line or course leading abruptly away from the usual course.

逸出常轨之线或路。

In a right-angled triangle, the ratio between the side opposite and the side adjacent to an acute angle; one of the trigonometric functions.

【数】直角三角形中，锐角之对边与其邻边之比；正切。