sit in vs attend

sit in and attend both are verbs.

Word	Noun	Adjective	Verb	Adverb
sit in	No	No	Yes	No
attend	No	No	Yes	No

As verbs, attend is a hypernym of sit in; that is, attend is a word with a broader meaning than sit in:

Other hypernyms of sit in include go to.

sit in (verb)	attend (verb)
participate in an act of civil disobedience	give heed (to)
attend as a visitor	work for, or be a servant to
	take charge of or deal with
	be present at (meetings, church services, university), etc.
	to accompany as a circumstance or follow as a result