| Transparency (social) | Transparency and translucency | Transparency International |
| Transplant rejection | Transponder (aeronautics) | Transport |
| Transport for London | Transport in Algeria | Transport in Cairo |
| Transport in Egypt | Transport in France | Transport in India |
| Transport in Iraq | Transport in Italy | Transport in Jordan |
| Transport in Kuwait | Transport in Lebanon | Transport in Libya |
| Transport in Morocco | Transport in Qatar | Transport in Russia |
| Transport in Saudi Arabia | Transport in Sudan | Transport in the Netherlands |
| Transport in the United Arab Emirates | Transport in Tunisia | Transport in Yemen |
| Transport layer | Transport Layer Security | Transport Ministry (Algeria) |
| Transport network | Transport phenomena | Transport vesicle |
| Transportation | Transportation engineering | Transportation geography |
| Transporter 2 | Transporter 3 | Transporter bridge |
| Transposable element | Transposase | Transposing instrument |
| Transposition of the great vessels | Transpyloric plane | Transsexual |
| Transtek | Transtheoretical theory | Transuranium element |
| Transversalis fascia | Transverse abdominal muscle | Transverse costal facet |
| Transverse facial artery | Transverse intermuscular septum | Transverse muscle of tongue |
| Transverse myelitis | Transverse plane | Transverse wave |
| Transvestism | Transylvania | Trap (plumbing) |
| Trapa natans | Trapdoor | Trapelus flavimaculatus |
| Trapelus mutabilis | Trapelus pallidus | Trapelus savignii |
| Trapezium (bone) | Trapezium Cluster | Trapezius muscle |
| Trapezoid | Trapezoid bone | Trapp mixture |
| Trappe, Maryland | Trapped (2002 film) | Traudl Junge |
| Trauma triad of death | Traumatic alopecia | Traumatic bonding |
| Traumatic bone cyst | Traumatic brain injury | Traumatocampa bonjeani |
| Trautv. | Travacò Siccomario | Travel agency |
| Travel literature | Travel Scholarships | Travel Service (airline) |
| Travel website | Traveler's diarrhea | Traveler's dilemma |
| Travelers Rest, South Carolina | Traveling-wave tube | Traveller's Tales |
| Travelling salesman problem | Traverse City, Michigan | Travertine |
| Travian | Travis Hansen | Travis Tomko |
| Travis Wear | Travis Willingham | Traylor Howard |
| Trazodone | Très Riches Heures du Duc de Berry | Trésor Mputu |
| Três Lagoas | Trần Đức Lương | Trümmerfrau |
| Tržič | Trbovlje | Treacher Collins syndrome |
| Treasure | Treasure Buddies | Treasure hunting |
| Treasure Island | Treasure Island (1920 film) | Treasure Island (1934 film) |
| Treasure Island (1950 film) | Treasure Island (1972 film) | Treasure Island (1990 film) |
| Treasure Island, Florida | Treasure Planet | Treasurer |
| Treasury | Treasury stock | Treat Williams |
| Treatment and control groups | Treaty | Treaty of Adrianople (1829) |
| Treaty of Brest-Litovsk | Treaty of Bucharest (1918) | Treaty of Hamedan |
| Treaty of Hudaybiyyah | Treaty of Küçük Kaynarca | Treaty of Manila (1946) |
| Treaty of Neuilly-sur-Seine | Treaty of Ouchy | Treaty of Rio de Janeiro (1825) |
| Treaty of Saint-Germain-en-Laye (1919) | Treaty of Sèvres | Treaty of the Pruth |
| Treaty of Tientsin | Treaty of Trianon | Treaty of Tripoli |
| Treaty of Versailles | Treaty on Open Skies | Treaty on the Non-Proliferation of Nuclear Weapons |
| Treaty with Algiers (1815) | Trebeta | Treble (sound) |
| Trebnje | Trebonianus Gallus | Trebuchet |
| TREC | Trechinae | Trechnotheria |
| Trechus | Trechus acuticollis | Trechus aethiopicus |
| Trechus albanicus | Trechus amicorum | Trechus amplicollis |
| Trechus angusticeps | Trechus apicalis | Trechus aquilus |
| Trechus armenus | Trechus artemisiae | Trechus asiaticus |
| Trechus chinensis | Trechus conformis | Trechus dilutus |
| Trechus egregius | Trechus grenieri | Trechus kashgarensis |
| Trechus lallemantii | Trechus markakolensis | Trechus mitchellensis |
| Trechus myanmarensis | Trechus namtsoensis | Trechus nebulosus |
| Trechus oregonensis | Trechus pallens | Trechus pumilus |
| Trechus rubens | Trechus subtilis | Trechus turkestanicus |
| Trechus turukensis | Trechus umbricola | Trechus verus |
| Tree | Tree (data structure) | Tree of life (biblical) |
| Tree of Life Web Project | Tree of the knowledge of good and evil | Tree planting |
| Tree-kangaroo | Treeshrew | Treg Brown |
| Trego, Wisconsin | Trel. | Trema |
| Trema integrifolia | Trema orientalis | Tremarctos Ornatus |
| Tremarctos ornatus | Trematoda | TrEMBL |
| Tremella mesenterica | Tremissis | Tremoctopus |
| Tremoctopus violaceus | Tremont City, Ohio | Tremont, Illinois |
| Tremont, Mississippi | Tremonton, Utah | Tremor |
| Trempealeau County, Wisconsin | Trempealeau, Wisconsin | Trenčianske Teplice |
| Trench | Trench coat | Trench warfare |
| Trendelenburg position | Trends in International Mathematics and Science Study | Trent Sainsbury |
| Trent, South Dakota | Trenton, Dodge County, Wisconsin | Trenton, Florida |
| Trenton, Georgia | Trenton, Illinois | Trenton, Kentucky |
| Trenton, Michigan | Trenton, Nebraska | Trenton, New Jersey |
| Trenton, Ohio | Trenton, Pierce County, Wisconsin | Trenton, Tennessee |
| Trenton, Texas | Trenton, Utah | Trenton, Washington County, Wisconsin |
| Treo 600 | Treo 650 | Treo 680 |
| Treo 755p | Trepanning | Treponema pallidum |
| Treron bicinctus | Treron capellei | Treron curvirostra |
| Treron olax | Treron phoenicoptera | Treron phoenicopterus |
| Treron sieboldii | Treron vernans | Treron waalia |
| Tres Cantos | TrES-4 | TrES-4b |
| Trescault | Trespaderne | Tressor Moreno |
| Tretinoin | Trevor Ariza | Trevor Brooking |
| Trevor Carson | Trevor Cherry | Trevor Devall |
| Trevor Donovan | Trevor Francis | Trevor Sinclair |
| Trevor Steven | Trevorite | Trey Parker |
| Treyarch | Treynor, Iowa | Trezevant, Tennessee |
| TRH | Tri-Ace | TRIAC |
| Triacetate | Triacontane | Triacylglycerol lipase |
| Triad (underground society) | Triadelphia, West Virginia | Triadophlebioptera |
| Triakidae | Trial and error | Trial by combat |
| Trial by media | Trial division | Trial of the century |
| Trial separation | Triangle | Triangle center |
| Triangle inequality | Triangle model | Triangle of auscultation |
| Triangle wave | Triangular interval | Triangular prism |
