P vs p

P and p both are nouns.

Word	Noun	Adjective	Verb	Adverb
P	Yes	No	No	No
p	Yes	No	No	No

As nouns, P and p are synonyms defined as:

P (noun)	p (noun)
the 16th letter of the Roman alphabet	the 16th letter of the Roman alphabet
a multivalent nonmetallic element of the nitrogen family that occurs commonly in inorganic phosphate rocks and as organic phosphates in all living cells; is highly reactive and occurs in several allotropic forms