sneak in vs add

sneak in and add both are verbs.

Word	Noun	Adjective	Verb	Adverb
sneak in	No	No	Yes	No
add	No	No	Yes	No

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

Other hypernyms of sneak in include append, supply.

sneak in (verb)	add (verb)
insert casually	make an addition (to); join or combine or unite with others; increase the quality, quantity, size or scope of
enter surreptitiously	make an addition by combining numbers
	determine the sum of
	state or say further
	bestow a quality on
	constitute an addition