straight line vs vector

straight line and vector both are nouns.

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

As nouns, vector is a hyponym of straight line; that is, vector 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
vector: a straight line segment whose length is magnitude and whose orientation in space is direction

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

straight line (noun)	vector (noun)
a line traced by a point traveling in a constant direction; a line of zero curvature	(genetics) a virus or other agent that is used to deliver DNA to a cell
	a variable quantity that can be resolved into components
	any agent (person or animal or microorganism) that carries and transmits a disease
	a straight line segment whose length is magnitude and whose orientation in space is direction