straight line vs bias

straight line and bias both are nouns.

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

As nouns, bias is a hyponym of straight line; that is, bias is a word with a more specific, narrower meaning than straight line:

straight line: a line traced by a point traveling in a constant direction; a line of zero curvature
bias: a line or cut across a fabric that is not at right angles to a side of the fabric

Other hyponyms of straight line include perpendicular, asymptote, tangent, secant, radius, diameter, chord, element, diagonal, diagonal, vector.

straight line (noun)	bias (noun)
a line traced by a point traveling in a constant direction; a line of zero curvature	a partiality that prevents objective consideration of an issue or situation
	a line or cut across a fabric that is not at right angles to a side of the fabric

straight line (adjective)	bias (adjective)
	slanting diagonally across the grain of a fabric

straight line (verb)	bias (verb)
	cause to be biased
	influence in an unfair way