polish vs improve

polish is a noun but improve is not a noun.

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

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

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

polish (noun)	improve (noun)
the property of being smooth and shiny
a highly developed state of perfection; having a flawless or impeccable quality
a preparation used in polishing

polish (verb)	improve (verb)
bring to a highly developed, finished, or refined state	get better
improve or perfect by pruning or polishing	to make better
make (a surface) shine