| | 4GL | | Fourth Generation Language |
| | 4rtd | | Four-Resonant-Tunneling-Diode |
| | EGBDF | | for remembering notes on a treble cleft music staff |
| | F&M | | Foot and Mouth |
| | f.a.r.t. | | Fugitive Apprehension Response Team |
| | f.a.t. | | file allocation table |
| | f.b.b.f.f. | | Facebook best friend forever |
| | F.D.D. | | floppy disk drive |
| | F.D.R.O.T.F.L.M.A.O. | | Falling Down Rolling On The Floor Laughing My ass off |
| | F.D.S.H. | | Full dealer service history |
| | f.e.a.e. | | forever and ever |
| | F.E.I.T.C.T.A.J. | | Forget them If They Can not Take A Joke |
| | F.F.O. | | for food only |
| | F.F.O. | | Funds from Operations |
| | F.F.U. | | falling for you |
| | f.f.w.f. | | Fight Fire With Fire |
| | F.M.P.E. | | From My Personal Experience |
| | f.m.t.y.e.w.t.k. | | Far More Than You Ever Wanted to Know |
| | F.N.A.R. | | For No Apparent Reason |
| | F.O.C.R.O.F.L.M.A.O. | | Falling Off Chair, Rolling on Floor, Laughing My Ass Off |
| | F.O.I.L. | | First Outer Inner last |
| | f.o.t.f.l.m.f.b.a.o. | | falling on the floor laughing my big ass off |
| | F.R.O.G. | | finished room over garage |
| | F.R.O.G. | | Frequency-resolved optical gating |
| | F.R.O.G. | | Fully Rely on God |
| | f.t.c. | | federal trade commission |
| | f.t.f. | | face to face |
| | F.T.K.A. | | Failed to Keep Appointment |
| | F.T.L.O. | | For The Love Of |
| | F.U.C.K. | | fornication under consent of the king |
|