asymptote

/ˌæsəm(p)ˈtoʊt/

Other forms: asymptotes

In geometry, an asymptote of a curve is a straight line that gets closer and closer but never touches the curve. An asymptote is sometimes called a tangent.

This is a term you're most likely to come across in math class. An asymptote is a straight line, but specifically one that approaches or nears a curve but never meets it. The noun asymptote has been a geometry term since the 1600's, and it comes from the Greek root asymptotos, or "not falling together," which combines a, "not," syn, "with," and ptotos, "fallen."

Definitions of asymptote

1. noun

   a straight line that is the limiting value of a curve; can be considered as tangent at infinity
   “the asymptote of the curve”

   type of:

   straight line

   a line traced by a point traveling in a constant direction; a line of zero curvature