gain vs sack up

gain is a noun but sack up is not a noun.

Word	Noun	Adjective	Verb	Adverb
gain	Yes	No	Yes	No
sack up	No	No	Yes	No

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

Other hyponyms of gain include cash in on, profiteer, capitalise, capitalize, take advantage, pyramid, clear, net, sack.

gain (noun)	sack up (noun)
the amount of increase in signal power or voltage or current expressed as the ratio of output to input
the advantageous quality of being beneficial
the amount by which the revenue of a business exceeds its cost of operating
a quantity that is added

gain (verb)	sack up (verb)
increase (one's body weight)	make as a net profit
rise in rate or price
increase or develop
obtain advantages, such as points, etc.
reach a destination, either real or abstract
earn on some commercial or business transaction; earn as salary or wages
win something through one's efforts
derive a benefit from
obtain