sailor boy vs Navy SEAL

sailor boy and Navy SEAL both are nouns.

Word	Noun	Adjective	Verb	Adverb
sailor boy	Yes	No	No	No
Navy SEAL	Yes	No	No	No

As nouns, Navy SEAL is a hyponym of sailor boy; that is, Navy SEAL is a word with a more specific, narrower meaning than sailor boy:

sailor boy: a serviceman in the navy
Navy SEAL: a member of a Naval Special Warfare unit who is trained for unconventional warfare

Other hyponyms of sailor boy include coastguardsman, SEAL, striker, submariner.

sailor boy (noun)	Navy SEAL (noun)
a serviceman in the navy	a member of a Naval Special Warfare unit who is trained for unconventional warfare