reimbursement vs costs

reimbursement and costs both are nouns.

Word	Noun	Adjective	Verb	Adverb
reimbursement	Yes	No	No	No
costs	Yes	No	No	No

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

reimbursement: compensation paid (to someone) for damages or losses or money already spent etc.
costs: pecuniary reimbursement to the winning party for the expenses of litigation

Other hyponyms of reimbursement include allowance, breakage.

reimbursement (noun)	costs (noun)
compensation paid (to someone) for damages or losses or money already spent etc.	pecuniary reimbursement to the winning party for the expenses of litigation