Wordnet 3.0
NOUN (1)
1. 
 a nonmetallic univalent element belonging to the halogens; 
 usually a yellow irritating toxic flammable gas; 
 a powerful oxidizing agent; 
 recovered from fluorite or cryolite or fluorapatite; 
[syn: fluorine, F, atomic number 9]
WordNet (r) 3.0 (2006):
atomic number 9
    n 1: a nonmetallic univalent element belonging to the halogens;
         usually a yellow irritating toxic flammable gas; a powerful
         oxidizing agent; recovered from fluorite or cryolite or
         fluorapatite [syn: fluorine, F, atomic number 9]