| 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 |
| Triangular theory of love | Triangulation | Triangulum |
| Triangulum Galaxy | Triarchic theory of intelligence | Triassic–Jurassic extinction event |
| Triatomic hydrogen | Triaxial shear test | Triazole |
| Tribadism | TribalWars | Tribe (biology) |
| Tribeca Film Festival | Tribology | Tribonyx mortierii |
| Tribonyx ventralis | Tribosphenida | Tribromometacresol |
| Tribulations of a Chinaman in China | Tribuloideae | Tribune |
| Tribune, Kansas | Tricalcium phosphate | Tricarbon |
| Triceps | Triceps brachii muscle | Triceratiales |
| Triceratops | Trichamoeba | Trichechidae |
| Trichechus | Trichechus inunguis | Trichechus manatus |
| Trichechus pygmaeus | Trichechus senegalensis | Trichiasis |
| Trichinella | Trichinella spiralis | Trichinosis |
| Trichiuridae | Trichlormethan | Trichobilharzia regenti |
| Trichodesmium | Trichogaster chuna | Trichogaster lalius |
| Trichogaster leerii | Trichogaster microlepis | Trichogaster pectoralis |
| Trichogaster trichopterus | Trichoglossus | Trichoglossus haematodus |
| Trichoglossus ornatus | Tricholoma | Tricholoma matsutake |
| Tricholomataceae | Trichomonas | Trichomonas vaginalis |
| Trichomycteridae | Trichophilia | Trichophyton |
| Trichophyton rubrum | Trichoplax | Trichoptera |
| Trichosantheae | Trichosanthes | Trichosanthes cordata |
| Trichosanthes cucumerina | Trichosanthes dioica | Trichosanthes dunniana |
| Trichosanthes kirilowii | Trichosanthes pilosa | Trichosanthes truncata |
| Trichosanthes wallichiana | Trichosporon | Trichostigma octandrum |
| Trichosurus vulpecula | Trichotillomania | Trichromacy |
| Trichuriasis | Trichuris trichiura | Trick or Treat |
| Tricladida | Triclinic | Triclinic crystal system |
| Tricolour (flag) | Triconex | Tricosane |
| Tricuspid | Tricuspid insufficiency | Tricuspid valve |
| Tricuspid valve stenosis | Tricyclic antidepressant | Tridacna (Tridacna) gigas |
| Tridacna gigas | Tridacna maxima | Tridecagon |
| Tridecane | Trident | Trident (layout engine) |
| Triembach-au-Val | Trienio Liberal | Trieste |
| Triethylaluminium | Trifid Nebula | Trifolieae |
| Trifolium | Trifolium acutiflorum | Trifolium aintabense |
| Trifolium alexandrinum | Trifolium angustifolium | Trifolium argutum |
| Trifolium arvense | Trifolium aureum | Trifolium berytheum |
| Trifolium bocconei | Trifolium boissieri | Trifolium bullatum |
| Trifolium campestre | Trifolium caucasicum | Trifolium cherleri |
| Trifolium clusii | Trifolium clypeatum | Trifolium constantinopolitanum |
| Trifolium dasyurum | Trifolium dichroanthum | Trifolium echinatum |
| Trifolium eriosphaerum | Trifolium fragiferum | Trifolium glanduliferum |
| Trifolium glomeratum | Trifolium grandiflorum | Trifolium haussknechtii |
| Trifolium hirtum | Trifolium hybridum | Trifolium incarnatum |
| Trifolium lappaceum | Trifolium ligusticum | Trifolium micranthum |
| Trifolium nigrescens | Trifolium ochroleucon | Trifolium palaestinum |
| Trifolium pauciflorum | Trifolium pilulare | Trifolium plebeium |
| Trifolium pratense | Trifolium purpureum | Trifolium repens |
| Trifolium resupinatum | Trifolium salmoneum | Trifolium spumosum |
| Trifolium squamosum | Trifolium squarrosum | Trifolium stellatum |
| Trifolium subterraneum | Trifolium suffocatum | Trifolium sylvaticum |
| Trifolium vavilovii | Trifon Ivanov | Triforce |
| Trifurcula ridiculosa | TRIGA | Trigeminal nerve |
