dig vs catch on

dig is a noun but catch on is not a noun.

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

As verbs, catch on is a hyponym of dig; that is, catch on is a word with a more specific, narrower meaning than dig:

Other hyponyms of dig include figure, cotton on, get it, get onto, get wise, latch on, tumble, twig, intuit, digest.

dig (noun)	catch on (noun)
the act of digging
the act of touching someone suddenly with your finger or elbow
a small gouge (as in the cover of a book)
an aggressive remark directed at a person like a missile and intended to have a telling effect
the site of an archeological exploration

dig (verb)	catch on (verb)
get the meaning of something	become popular
turn up, loosen, or remove earth	understand, usually after some initial difficulty
create by digging
remove the inner part or the core of
poke or thrust abruptly
thrust down or into
remove, harvest, or recover by digging
work hard