vector sum vs vector

vector sum and vector both are nouns.

Word	Noun	Adjective	Verb	Adverb
vector sum	Yes	No	No	No
vector	Yes	No	No	No

As nouns, vector is a hypernym of vector sum; that is, vector is a word with a broader meaning than vector sum:

vector sum (noun)	vector (noun)
a vector that is the sum of two or more other vectors	(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