fit in vs concord

fit in is not a noun while concord is a noun.

Word	Noun	Adjective	Verb	Adverb
fit in	No	No	Yes	No
concord	Yes	No	Yes	No

As verbs, fit in and concord are synonyms defined as:

Other synonyms of fit in include accord, agree, consort, harmonise, harmonize.

fit in (noun)	concord (noun)
	agreement of opinions
	the determination of grammatical inflection on the basis of word relations
	a harmonious state of things in general and of their properties (as of colors and sounds); congruity of parts with one another and with the whole

fit in (verb)	concord (verb)
go together	be in accord; be in agreement
	arrange the words of a text so as to create a concordance
	arrange by concord or agreement
	go together