# What is the term for a line that doesn't touch a function?

A line that cuts into a function is a secant line, and a line that just touches a function is a tangent line.

But what is the term for a line that does not touch the function?

Take the parabola: $$y=x^2$$

A secant line would be: $y=2$

A tangent line would be: $y=0$

But what would $y=-2$ be ?

This line does have a special name as I remember reading it somewhere before and being surprised that it had a name. But unfortunately I have since forgotten it.

I keep thinking extraneous line but I can't find that term anywhere in writing.

• I really doubt that it has a name. It doesn't feel useful or significant enough. There may be some archaic term somewhere though. – Arthur Aug 20 '18 at 13:48
• I thought that before too, but I came across its name a while ago but have since forgotten it. I'm fairly sure it does have a name. – Kantura Aug 20 '18 at 13:50
• We can say "non-intersecting line". – user Aug 20 '18 at 13:52
• Were you meaning asymptote? – Mohammad Zuhair Khan Aug 20 '18 at 15:03