seriously vs severely

seriously and severely both are adverbs.

Word	Noun	Adjective	Verb	Adverb
seriously	No	No	No	Yes
severely	No	No	No	Yes

As adverbs, seriously and severely are synonyms defined as:

Other synonyms of seriously include badly, gravely.

seriously (adverb)	severely (adverb)
in a serious manner	to a severe or serious degree
to a severe or serious degree	with sternness; in a severe manner
	causing great damage or hardship