argot vs patois

argot and patois both are nouns.

Word	Noun	Adjective	Verb	Adverb
argot	Yes	No	No	No
patois	Yes	No	No	No

As nouns, argot and patois are synonyms defined as:

argot and patois: a characteristic language of a particular group (as among thieves)

Other synonyms of argot include cant, jargon, lingo, slang, vernacular.

argot (noun)	patois (noun)
a characteristic language of a particular group (as among thieves)	a regional dialect of a language (especially French); usually considered substandard
	a characteristic language of a particular group (as among thieves)