phosphorus

Short definition from Wiktionary

Noun

1. 1
   a chemical element (symbol P) with an atomic number of 15, that exists in several allotropic forms.
2. 2
   any substance exhibiting phosphorescence; a phosphor.

Proper noun

1. 1
   A name sometimes used for Hesperus, the personification in Greek mythology of the planet Venus.
2. 2
   An Ancient Greek name for the morning star (the planet Venus when it is visible in the eastern sky before sunrise).