- 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 - morning star, daystar, Phosphorus - a planet (usually Venus) seen just before sunrise in the eastern sky
--2 is a kind of planet