but vs simply

but and simply both are adverbs.

Word	Noun	Adjective	Verb	Adverb
but	No	No	No	Yes
simply	No	No	No	Yes

As adverbs, but and simply are synonyms defined as:

Other synonyms of but include just, merely, only.

but (adverb)	simply (adverb)
and nothing more	and nothing more
	in a simple manner; without extravagance or embellishment
	absolutely; altogether; really
	(used for emphasis) absolutely