sailor vs serviceman

sailor and serviceman both are nouns.

Word	Noun	Adjective	Verb	Adverb
sailor	Yes	No	No	No
serviceman	Yes	No	No	No

As nouns, serviceman is a hypernym of sailor; that is, serviceman is a word with a broader meaning than sailor:

sailor: a serviceman in the navy
serviceman: someone who serves in the armed forces; a member of a military force

Other hypernyms of sailor include man, military man, military personnel.

sailor (noun)	serviceman (noun)
a stiff hat made of straw with a flat crown	someone who serves in the armed forces; a member of a military force
any member of a ship's crew
a serviceman in the navy