| Acronym | Meaning |
| FINDS | Facilities Index Data System |
| FINES | Furnace Ionization Nonthermal Excitation Spectrometry |
| FINS | Forensically Informative Nucleotide Sequencing |
| FIOH | Finnish Institute Of Occupational Health |
| FIOR | Fluid Iron Ore Reduction |
| FIP | First Ionization Potential |
| FIP | Flow Injection Potentiometry |
| FIP | Full Intra-pair (spin-coupling) (wave Function) |
| FIPS | Federal Information Processing Standard |
| FIRE | Flame Infrared Emission |
| FIRF | Finite Impulse Response Filter |
| FIRFT | Fast Inversion-recovery Fourier Transform |
| FIRMR | Federal Information Resources Management Regulations |
| FIRST | Field-portable Imaging Radiometric Spectrometer Technology |
| FIRST | Faint Images Of The Radio Sky At Twenty Centimeters |
| FIRST | Far Infrared And Submillimetre Space Telescope |
| FIS | Field Ion Spectroscopy |
| FISCI | Final Ionic State Configuration Interaction |
| FISH | Fluorescence In Situ Hybridization |
| FISP | Fast Imaging With Steady-state Precession |
| FIT | Field Investigation Team (US EPA) |
| FIT | Flow Injection Titration |
| FITC | Fluorescein Isothiocyanate |
| FIV | Feline Immunodeficiency Virus |
| FK | Fish Kill (file Within STORET) |
| FKBP | FK506 Binding Protein |
| FKN | Field-Koros-Noyes (mechanism) |
| FKO | Franz-Keldish Oscillations |
| FLA | Fluorescence Lifetime Analysis |
| FLAA | Flame Atomic Absorption |
| FLAIR | Fluid Attenuated Infrared Sequence |
| FLAIR | Fluid Attenuated Inversion Recovery |
| FLAP | 5-lipoxygenase-activating Protein |
| FLAPW | Full-potential Linearized Augmented Plane Wave |
| FLASH | Fast Low-angle Shot (NMR Imaging) |
| FLASH | Fluorescent Airborne Stratospheric Hygrometer |
| FLC | Ferroelec. Liq. Crystal |
| FLCAO | Factorized LCAO |
| FLCD | Ferroelectric Liquid Crystal Display |
| FLD | Forming Limit Diagram |
| FLDA | Fuzzy Linear Discriminant Analysis |
| FLIM | Fluorescence Lifetime Imaging Microscopy |
| FLIP | FLICE-inhibitory Protein |
| FLIPR | Fluorescent Imaging Plate Reader |
| FLIR | Forward-looking Infrared |
| FLISA | Fluorescence-linked Immunosorbent Assay |
| FLMS | Femtosecond Laser Mass Spectrometry |
| FLMTO | Film Linearized Muffin-tin Orbital (for Surface Electronic Structure Calcns.) |
| FLN | Fluorescence Line Narrowing |
| FLNS | Fluorescence Line-narrowing Spectroscopy |