interest vs concern

interest and concern both are nouns.

Word	Noun	Adjective	Verb	Adverb
interest	Yes	No	Yes	No
concern	Yes	No	Yes	No

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

interest: a sense of concern with and curiosity about someone or something
concern: something that interests you because it is important or affects you

Other hyponyms of interest include enthusiasm.

As verbs, concern is a hypernym of interest; that is, concern is a word with a broader meaning than interest:

Other hypernyms of interest include bear on, come to, have to do with, pertain, refer, relate, touch, touch on.

As verbs, interest and concern are synonyms defined as:

Other synonyms of interest include occupy, worry.

interest (noun)	concern (noun)
a diversion that occupies one's time and thoughts (usually pleasantly)	something that interests you because it is important or affects you
a reason for wanting something done	something or someone that causes anxiety; a source of unhappiness
the power of attracting or holding one's attention (because it is unusual or exciting etc.)	a feeling of sympathy for someone or something
a sense of concern with and curiosity about someone or something	an anxious feeling
(usually plural) a social group whose members control some field of activity and who have common aims	a commercial or industrial enterprise and the people who constitute it
a fixed charge for borrowing money; usually a percentage of the amount borrowed
(law) a right or legal share of something; a financial involvement with something

interest (verb)	concern (verb)
excite the curiosity of; engage the interest of	be relevant to
be of importance or consequence	be on the mind of
be on the mind of