build vs improve

build is a noun but improve is not a noun.

Word	Noun	Adjective	Verb	Adverb
build	Yes	No	Yes	No
improve	No	No	Yes	No

As verbs, improve is a hypernym of build; that is, improve is a word with a broader meaning than build:

Other hypernyms of build include ameliorate, amend, better, meliorate.

build (noun)	improve (noun)
constitution of the human body
alternative names for the body of a human being

build (verb)	improve (verb)
form or accumulate steadily	get better
improve the cleansing action of	to make better
bolster or strengthen
develop and grow
found or ground
make by combining materials and parts
give form to, according to a plan
build or establish something abstract
be engaged in building
order, supervise, or finance the construction of