innings vs follow-on

innings and follow-on both are nouns.

Word	Noun	Adjective	Verb	Adverb
innings	Yes	No	No	No
follow-on	Yes	No	No	No

As nouns, follow-on is a hyponym of innings; that is, follow-on is a word with a more specific, narrower meaning than innings:

innings: the batting turn of a cricket player or team
follow-on: an immediate second innings forced on a cricket team scoring a prescribed number of runs fewer than its opponents in the first innings

innings (noun)	follow-on (noun)
the batting turn of a cricket player or team	an immediate second innings forced on a cricket team scoring a prescribed number of runs fewer than its opponents in the first innings