- (
geometry 幾何 a straight line that touches the outside of a curve but does not cross it 切線 
The cart track branches off at a tangent. 大車軌道在切線處分叉。
- (abbreviation tan)(
mathematics 數學 the ratio of the length of the side opposite an angle in a right-angled triangle to the length of the side next to it 正切
Word Originlate 16th cent. (in sense (2) and as an adjective): from Latin tangent- ‘touching’, from the verb tangere.
Idioms
fly/go off at a tangent (British English)
(North American English go off on a tangent)
- (informal)
to suddenly start saying or doing something that does not seem to be connected to what has gone before 突然轉換話題；突然改變行動 He never sticks to the point but keeps going off at a tangent. 他從來不堅持要點，而是一直離題。 Laura’s mind went off at a tangent. 勞拉心不在焉。