mariner vs seaman

mariner and seaman both are nouns.

Word	Noun	Adjective	Verb	Adverb
mariner	Yes	No	No	No
seaman	Yes	No	No	No

As nouns, mariner and seaman are synonyms defined as:

Other synonyms of mariner include gob, Jack-tar, Jack, old salt, sea dog, seafarer, tar.

mariner (noun)	seaman (noun)
a man who serves as a sailor	a man who serves as a sailor