gain vs increase

gain and increase both are nouns.

Word	Noun	Adjective	Verb	Adverb
gain	Yes	No	Yes	No
increase	Yes	No	Yes	No

As nouns, increase is a hypernym of gain; that is, increase is a word with a broader meaning than gain:

gain: the amount of increase in signal power or voltage or current expressed as the ratio of output to input
increase: the amount by which something increases

Other hypernyms of gain include increment.

As nouns, gain and increase are synonyms defined as:

Other synonyms of gain include addition.

As verbs, increase is a hypernym of gain; that is, increase is a word with a broader meaning than gain:

gain (noun)	increase (noun)
the amount of increase in signal power or voltage or current expressed as the ratio of output to input	the act of increasing something
the advantageous quality of being beneficial	the amount by which something increases
the amount by which the revenue of a business exceeds its cost of operating	a change resulting in an increase
a quantity that is added	a process of becoming larger or longer or more numerous or more important
	a quantity that is added

gain (verb)	increase (verb)
increase (one's body weight)	become bigger or greater in amount
rise in rate or price	make bigger or more
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