P.O. vs SCPO

P.O. and SCPO both are nouns.

Word	Noun	Adjective	Verb	Adverb
P.O.	Yes	No	No	No
SCPO	Yes	No	No	No

As nouns, SCPO is a hyponym of P.O.; that is, SCPO is a word with a more specific, narrower meaning than P.O.:

P.O.: a noncommissioned officer in the Navy or Coast Guard with a rank comparable to sergeant in the Army
SCPO: a senior noncommissioned officer in the Navy or Coast Guard with a rank comparable to master sergeant in the Army

Other hyponyms of P.O. include master-at-arms, senior chief petty officer.

P.O. (noun)	SCPO (noun)
a noncommissioned officer in the Navy or Coast Guard with a rank comparable to sergeant in the Army	a senior noncommissioned officer in the Navy or Coast Guard with a rank comparable to master sergeant in the Army