separate vs split up

separate and split up both are nouns.

Word	Noun	Adjective	Verb	Adverb
separate	Yes	Yes	Yes	No
split up	Yes	No	Yes	No

As verbs, separate and split up are synonyms defined as:

Other synonyms of separate include break, come apart, fall apart.

As verbs, separate and split up are synonyms defined as:

Other synonyms of separate include carve up, dissever, divide, split.

As verbs, separate and split up are synonyms defined as:

separate and split up: discontinue an association or relation; go different ways

Other synonyms of separate include break, break up, part, split.

As verbs, split up is a hyponym of separate; that is, split up is a word with a more specific, narrower meaning than separate:

separate (noun)	split up (noun)
a garment that can be purchased separately and worn in combinations with other garments	an increase in the number of outstanding shares of a corporation without changing the shareholders' equity
a separately printed article that originally appeared in a larger publication

separate (adjective)	split up (adjective)
independent; not united or joint
standing apart; not attached to or supported by anything
separated according to race, sex, class, or religion
have the connection undone; having become separate

separate (verb)	split up (verb)
become separated into pieces or fragments	become separated into pieces or fragments
divide into two or more branches so as to form a fork	get a divorce; formally terminate a marriage
arrange or order by classes or categories	discontinue an association or relation; go different ways
mark as different	separate into parts or portions
move or break apart
force, take, or pull apart
divide into components or constituents
go one's own way; move apart
make a division or separation
treat differently on the basis of sex or race
separate into parts or portions
discontinue an association or relation; go different ways
act as a barrier between; stand between