marquis vs marquess

marquis and marquess both are nouns.

Word	Noun	Adjective	Verb	Adverb
marquis	Yes	No	No	No
marquess	Yes	No	No	No

As nouns, marquis and marquess are synonyms defined as:

marquis and marquess: nobleman (in various countries) ranking above a count

marquis (noun)	marquess (noun)
nobleman (in various countries) ranking above a count	a British peer ranking below a duke and above an earl
	nobleman (in various countries) ranking above a count