run-in vs difference

run-in and difference both are nouns.

Word	Noun	Adjective	Verb	Adverb
run-in	Yes	No	No	No
difference	Yes	No	No	No

As nouns, difference is a hypernym of run-in; that is, difference is a word with a broader meaning than run-in:

Other hypernyms of run-in include conflict, difference of opinion, dispute.

run-in (noun)	difference (noun)
an angry dispute	the quality of being unlike or dissimilar
	a disagreement or argument about something important
	a variation that deviates from the standard or norm
	the number that remains after subtraction; the number that when added to the subtrahend gives the minuend
	a significant change