- phosphorus, P, atomic number 15 - 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
--1 is a kind of chemical element, element
--1 is a substance of apatite - P - the 16th letter of the Roman alphabet
--2 is a kind of letter, letter of the alphabet, alphabetic character
--2 is a member of Roman alphabet, Latin alphabet