fill in vs fill

fill in is not a noun while fill is a noun.

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

fill in (noun)	fill (noun)
	a quantity sufficient to satisfy
	any material that fills a space or container

fill in (verb)	fill (verb)
supply with information on a specific topic	become full
write all the required information onto a form	make full, also in a metaphorical sense
represent the effect of shade or shadow on	plug with a substance
be a substitute	fill to satisfaction
	eat until one is sated
	fill, satisfy or meet a want or need or condition or restriction
	assume, as of positions or roles
	appoint someone to (a position or a job)
	occupy the whole of