Tangent

In geometry, a tangent (or tangent line) to a curve at a given point is a straight line that touches but does not intersect the curve at that point. It can be defined as a line through a pair of infinitely close points on a curve.

  • A tangent to a circle at a given point is a line that touches but does not intersect the circle and is at right angles to radial line drawn from the point to the centre of the circle.

https://en.wikipedia.org/wiki/Tangent