interchange vs fill in

interchange is a noun but fill in is not a noun.

Word	Noun	Adjective	Verb	Adverb
interchange	Yes	No	Yes	No
fill in	No	No	Yes	No

As verbs, fill in is a hyponym of interchange; that is, fill in is a word with a more specific, narrower meaning than interchange:

Other hyponyms of interchange include sell, cash, cash in, ransom, redeem, redeem, stand in, sub, substitute, swap, switch, swop, trade, barter, trade, trade in.

interchange (noun)	fill in (noun)
the act of changing one thing for another thing
mutual interaction; the activity of reciprocating or exchanging (especially information)
reciprocal transfer of equivalent sums of money (especially the currencies of different countries)
a junction of highways on different levels that permits traffic to move from one to another without crossing traffic streams

interchange (verb)	fill in (verb)
reverse (a direction, attitude, or course of action)	supply with information on a specific topic
cause to change places	write all the required information onto a form
give to, and receive from, one another	represent the effect of shade or shadow on
put in the place of another; switch seemingly equivalent items	be a substitute