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 WordNet 3.0 & Open English WordNet

Fluorine is a chemical element; it has symbol F and atomic number 9. Wikipedia

Chemical element with symbol F and atomic number 9 Wikidata

A gaseous chemical element with symbol F and atomic number 9; a member of the halide family, it is the most electronegative element and the most chemically energetic of the nonmetallic elements; highly toxic and corrosive; used in rocket fuels and as a chemical intermediate. OmegaWiki

The chemical element (symbol F) with an atomic number of 9. It is the lightest of the halogens, a pale yellow-green, highly reactive gas that attacks all metals. Wiktionary

Chemical element. Wiktionary (translation)