| Abbreviation | Definition |
|---|---|
| FIM | Fiber Interface Module |
| FIM | Field Ion Microscopy |
| FiOS | Fiber Optic Service |
| FIR | Far InfraRed |
| FIR | Finite Impulse Response |
| FIRST | Floppy Inclusions and Rigid Substructure Topography |
| FIS | Fault Isolation System |
| FIT | Failure unIT |
| FIT | Filtering Integration Technology |
| FITK | Filter Inductor Torodial Kit |
| FITS | Functional Interpolation Transfer System |
| FKEC | Florida Keys Electric Cooperative |
| FL | Frequency Lock |
| FL | Fuzzy Logic |
| FLA | Fully Loaded Amperes |
| FLAM | Fault Location And Monitoring |
| FLAP | Failure Location Analysis Program |
| FLAPW | Full-potential Linearized Augmented Plane Wave |
| FLC | Forward LAN Channel |
| FLC | Full Load Current |