sure as shooting vs certainly

sure as shooting is an adjective but certainly is not an adjective.

Word	Noun	Adjective	Verb	Adverb
sure as shooting	No	Yes	No	Yes
certainly	No	No	No	Yes

As adverbs, sure as shooting and certainly are synonyms defined as:

sure as shooting and certainly: definitely or positively (`sure' is sometimes used informally for `surely')

Other synonyms of sure as shooting include for certain, for sure, sure, sure enough, surely.

sure as shooting (adjective)	certainly (adjective)
absolutely certain

sure as shooting (adverb)	certainly (adverb)
definitely or positively (`sure' is sometimes used informally for `surely')	definitely or positively (`sure' is sometimes used informally for `surely')