PO vs petty officer

PO and petty officer both are nouns.

Word	Noun	Adjective	Verb	Adverb
PO	Yes	No	No	No
petty officer	Yes	No	No	No

As nouns, PO and petty officer are synonyms defined as:

PO and petty officer: a noncommissioned officer in the Navy or Coast Guard with a rank comparable to sergeant in the Army

Other synonyms of PO include P.O..

PO (noun)	petty officer (noun)
an independent agency of the federal government responsible for mail delivery (and sometimes telecommunications) between individuals and businesses in the United States	a noncommissioned officer in the Navy or Coast Guard with a rank comparable to sergeant in the Army
a noncommissioned officer in the Navy or Coast Guard with a rank comparable to sergeant in the Army