vector vs vector sum

vector and vector sum both are nouns.

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

As nouns, vector sum is a hyponym of vector; that is, vector sum is a word with a more specific, narrower meaning than vector:

Other hyponyms of vector include cross product, vector product, resultant, radius vector, radius vector.

vector (noun)	vector sum (noun)
(genetics) a virus or other agent that is used to deliver DNA to a cell	a vector that is the sum of two or more other vectors
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