Source : Webster's Revised Unabridged Dictionary (1913)

F \F\ ([e^]f).
   1. F is the sixth letter of the English alphabet, and a
      nonvocal consonant. Its form and sound are from the Latin.
      The Latin borrowed the form from the Greek digamma ?,
      which probably had the value of English w consonant. The
      form and value of Greek letter came from the Ph[oe]nician,
      the ultimate source being probably Egyptian.
      Etymologically f is most closely related to p, k, v, and
      b; as in E. five, Gr. pe`nte; E. wolf, L. lupus, Gr.
      ly`kos; E. fox, vixen; fragile, break; fruit, brook, v.
      t.; E. bear, L. ferre. See Guide to Pronunciation,
      [sect][sect] 178, 179, 188, 198, 230.

   2. (Mus.) The name of the fourth tone of the model scale, or
      scale of C. F sharp (F [sharp]) is a tone intermediate
      between F and G.

   {F clef}, the bass clef. See under {Clef}.

Source : WordNet®

F
     n 1: a degree on the Fahrenheit scale of temperature [syn: {degree
          Fahrenheit}]
     2: 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}, {atomic number
        9}]
     3: the capacitance of a capacitor that has an equal and
        opposite charge of 1 coulomb on each plate and a voltage
        difference of 1 volt between the plates [syn: {farad}]
     4: the 6th letter of the Roman alphabet