goddam vs goddamn

goddam and goddamn both are adjectives.

Word	Noun	Adjective	Verb	Adverb
goddam	No	Yes	No	Yes
goddamn	No	Yes	No	Yes

As adjectives, goddam and goddamn are synonyms defined as:

Other synonyms of goddam include blame, blamed, blasted, blessed, damn, damned, darned, deuced, goddamned, infernal.

As adverbs, goddam and goddamn are synonyms defined as:

goddam and goddamn: expressing anger, despair, frustration, approval, or surprise

Other synonyms of goddam include goddamned.

goddam (adjective)	goddamn (adjective)
expletives used informally as intensifiers	used as expletives
	expletives used informally as intensifiers

goddam (adverb)	goddamn (adverb)
expressing anger, despair, frustration, approval, or surprise	expressing anger, despair, frustration, approval, or surprise