split up vs break away

split up is a noun but break away is not a noun.

Word	Noun	Adjective	Verb	Adverb
split up	Yes	No	Yes	No
break away	No	No	Yes	No

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

split up (noun)	break away (noun)
an increase in the number of outstanding shares of a corporation without changing the shareholders' equity

split up (verb)	break away (verb)
become separated into pieces or fragments	break off (a piece from a whole)
get a divorce; formally terminate a marriage	flee; take to one's heels; cut and run
discontinue an association or relation; go different ways	move away or escape suddenly
separate into parts or portions	withdraw from an organization or communion
	interrupt a continued activity