| Acronym | Meaning |
| FRS | Fragment Separatorpar |
| FRS | Forced Rayleigh Scattering |
| FRS | Forward Recoil Spectrometry |
| FRSS | Federal Register Search System |
| FRSW | Finite Range Scattering Wave Function |
| FRTP | Fiber-reinforced Thermoplastic |
| FS | Feasibility Study |
| FSA | Free And Saline Ammonia (e.g. |
| FSC | Fluorescent Solar Concentrator |
| FSCC | Fock Space Coupled Cluster |
| FSCE | Free-solution Capillary Electrophoresis |
| FSCT | Federation Of Societies For Coatings Technology |
| FSCV | Fast-scan Cyclic Voltammetry |
| FSE | Fast Spin Echo |
| FSG | Fluorosilicate Glass |
| FSGF | FREEON Symmetric Group Formulation (of Hartree-Fock Theory) |
| FSGO | Floating Spherical Gaussian Orbital |
| FSH | Follicle-stimulating Hormone |
| FSIS | Food Safety And Inspection Service |
| FSM | Folded-sheet Mesoporous Material |
| FSMRCC | Fock Space Multireference Coupled Cluster |
| FSMRCCSD | Fock Space Multireference Coupled Cluster (with) Single (and) Double Excitations |
| FSOT | Fused Silica Open Tubular |
| FSQ | Full-spectrum Quantitation |
| FSR | Fractional Synthesis Rate |
| FSR | Free Spectral Range |
| FSR | Fixed Salt Recovery (in Regeneration Of Blowdown From HCN Scrubber) |
| FSSW | Friction Super Stir Welding |
| FSTRAC | Federal-State Toxicology And Risk Analysis Committee |
| FTC | Federal Trade Commission |
| FTD | Flame Thermionic Detector (gas Chromatography) |
| FTD | Frontotemporal Dementia |
| FTEMIRS | Fourier Transform Electrochem. Modulated IR Spectroscopy |
| FTHF | Finite-temperature Hartree-Fock |
| FTHFB | Finite-temperature Hartree-Fock-Bogolyubov |
| FTICR | Fourier Transform Ion Cyclotron Resonance |
| FTICRMS | Fourier Transform Ion Cyclotron Resonance Mass Spectrometry |
| FTIR | Fourier Transform Infrared Spectroscopy |
| FTM | Fault Tree Model |
| FTMS | Fourier Transform Mass Spectrometry |
| FTNMR | Fourier-transform Nuclear Magnetic Resonance |
| FTP | US Federal Test Procedure (for Exhaust Catalysts) |
| FTR | Frustrated Total Reflection |
| FTS | Fourier Transform Spectroscopy |
| FTTA | Federal Technology Transfer Act |
| FTU | Formazine Turbidity Unit |
| FTVS | Fourier Transform Visible Spectroscopy |
| FUBAR | F(ouled) Up Beyond Recognition |
| FUGH | FREEON Unitary Group Formulation (of Hartree-Fock Theory) |
| FUMI | Function Of Mutual Information |