asymptote vs straight line

asymptote and straight line both are nouns.

Word	Noun	Adjective	Verb	Adverb
asymptote	Yes	No	No	No
straight line	Yes	No	No	No

As nouns, straight line is a hypernym of asymptote; that is, straight line is a word with a broader meaning than asymptote:

asymptote: a straight line that is the limiting value of a curve; can be considered as tangent at infinity
straight line: a line traced by a point traveling in a constant direction; a line of zero curvature

asymptote (noun)	straight line (noun)
a straight line that is the limiting value of a curve; can be considered as tangent at infinity	a line traced by a point traveling in a constant direction; a line of zero curvature