Pronunciation: (ef),[key] —n., —pl.F's or Fs, f's or fs. 1. the sixth letter of the English alphabet, a consonant.
2. any spoken sound represented by the letter F or f, as in fat, differ, or huff. 3. something having the shape of an F. 4. a written or printed representation of the letter F or f. 5. a device, as a printer's type, for reproducing the letter F or f.
—Symbol. 1. the sixth in order or in a series.
2. (sometimes l.c.) (in some grading systems) a grade or mark that indicates academic work of the lowest quality; failure.
3. Music. a. the fourth tone in the scale of C major or the sixth tone in the relative minor scale, A minor.
b. a string, key, or pipe tuned to this tone.
c. a written or printed note representing this tone.
d. (in the fixed system of solmization) the fourth tone of the scale of C major, called fa. e. the tonality having F as the tonic note.
4. (sometimes l.c.) the medieval Roman numeral for 40. Cf. Roman numerals. 5. Math a. field.
b. function (of).
6. (sometimes l.c.)Elect.farad.
8. (sometimes l.c.)Physics. a. force.
2. Photog.See f-number. 3. Music.forte.
—Symbol,Optics. See focal length.
Mil. (in designations of aircraft) fighter: F-105.