Buddha vs Gautama Siddhartha

Buddha and Gautama Siddhartha both are nouns.

Word	Noun	Adjective	Verb	Adverb
Buddha	Yes	No	No	No
Gautama Siddhartha	Yes	No	No	No

As nouns, Buddha and Gautama Siddhartha are synonyms defined as:

Other synonyms of Buddha include Gautama, Gautama Buddha, Siddhartha.

Buddha (noun)	Gautama Siddhartha (noun)
founder of Buddhism (c 563-483 BC)	founder of Buddhism (c 563-483 BC)
one who has achieved a state of perfect enlightenment