tie up vs tie-up

tie up is not a noun while tie-up is a noun.

Word	Noun	Adjective	Verb	Adverb
tie up	No	No	Yes	No
tie-up	Yes	No	No	No

tie up (noun)	tie-up (noun)
	an interruption of normal activity
	a social or business relationship

tie up (verb)	tie-up (verb)
secure with or as if with ropes
finish the last row
restrain from moving or operating normally
secure in or as if in a berth or dock
invest so as to make unavailable for other purposes