straight line vs chord

straight line and chord both are nouns.

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

As nouns, chord is a hyponym of straight line; that is, chord 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
chord: a straight line connecting two points on a curve

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

straight line (noun)	chord (noun)
a line traced by a point traveling in a constant direction; a line of zero curvature	a combination of three or more notes that blend harmoniously when sounded together
	a straight line connecting two points on a curve

straight line (verb)	chord (verb)
	bring into consonance, harmony, or accord while making music or singing
	play chords on (a stringed instrument)