cotton on vs catch on

cotton on and catch on both are verbs.

Word	Noun	Adjective	Verb	Adverb
cotton on	No	No	Yes	No
catch on	No	No	Yes	No

As verbs, cotton on and catch on are synonyms defined as:

cotton on and catch on: understand, usually after some initial difficulty

Other synonyms of cotton on include get it, get onto, get wise, latch on, tumble, twig.

cotton on (verb)	catch on (verb)
understand, usually after some initial difficulty	become popular
	understand, usually after some initial difficulty