| Acronym | Meaning |
| SXPS | Soft X-ray Photoelectron Spectroscopy |
| SXRAM | Scanning X-ray Analytical Microprobe |
| SXRD | Surface X-ray Diffraction |
| SXRF | Synchrotron X-ray Fluorescence |
| SXRFM | Synchrotron X-ray-fluorescence Microprobe |
| SXRFMA | Synchrotron X-ray-fluorescence Microanalysis |
| SZA | Solar Zenith Angle |
| T-GAS | Trace Gas Accounting System |
| T-J MODEL | Heisenberg-Hubbard Model (Hamiltonian) |
| TAC | Toxic Air Contaminant |
| TAC | Total Antioxidn. Capacity |
| TACB | Texas Air Control Board |
| TACE | Tumor Necrosis Factor Alpha-converting Enzyme |
| TACI | Transmembrane Activator And CAML Interactor |
| TACT | Trans Alaska Crustal Transect |
| TAD | Thermophilic Aerobic Digestion (of Sewage Sludge) |
| TADAP | Transport And Deposition Of Acidifying Pollutants (European Environmental Model) |
| TAFE | Transverse Alternating-field Electrophoresis |
| TAFI | Thrombin Activatable Fibrinolysis Inhibitor |
| TAG | Trans-Atlantic Geotraverse |
| TAGGSI | Transfer Of Aerosols And Gases To The Greenland Snow And Ice |
| TAI | Thermal Alteration Index |
| TAL | Threshold Ambient Level |
| TALEST | Tandem Arrayed Ligation Of Expressed Sequence Tags |
| TALIF | Two-photon Absorption Laser Induced Fluorescence |
| TALMS | Tunable Atomic Line Molecular Spectroscopy |
| TAME | Tert-amyl Methyl Ether |
| TAMS | Toxic Air Monitoring System (US EPA) |
| TAMS | Tandem Accelerator Mass Spectrometry |
| TAN | Total Acid Number |
| TANGO | Testing For Adjacent Nuclei With A Gyration Operator |
| TAP | Temporal Anal. Of Products |
| TAP | Toxic Air Pollutant |
| TAPPI | Technical Association Of The Pulp And Paper Industry |
| TAPS | Tris-aminopropanesulfonic Acid |
| TARC | Tiered Area Response Capability |
| TARFOX | Tropospheric Aerosol Radiative Forcing Observation Experiment |
| TARIS | Thermal Atomization Resonance Ionization Spectrometry |
| TARP | Technical Assistance Response Program |
| TART | Tip-angle Reduced T1 Imaging |
| TAS | Total Analysis Systems |
| TASCC | Chalk River Tandem Accelerator Superconducting Cyclotron Facility |
| TASO | Terminal Atom Symmetry Orbital |
| TASP | Template-assembled Synthetic Proteins |
| TAT | Technical Assistance Team |
| TATP | Triacetone Triperoxide |
| TBA | Tight Binding Approximation |
| TBA | True Bicarbonate Activity |
| TBAB | Tetrabutylammonium Bromide |
| TBARS | Thiobarbituric Acid Reactive Substances |