| thinner | más enrarecido |
| thinning | dilución |
| Thiol | Tiol |
| Thionyl chloride | Cloruro de tionilo |
| thiosulfate | tiosulfato |
| Thiotimoline | Tiotimolina |
| thioxanthene | tioxanteno |
| third | tercero |
| Third Age | Tercera Edad del Sol |
| Third Amendment to the United States Constitution | Tercera Enmienda a la Constitución de los Estados Unidos |
| Third Battle of Kharkov | Tercera Batalla de Jarkov |
| Third Battle of the Aisne | Batalla de Axona |
| Third bridge guitar | Guitarra de tres puentes |
| Third Council of Constantinople | Tercer Concilio de Constantinopla |
| Third Council of the Lateran | Concilio de Letrán III |
| Third Council of Toledo | III Concilio de Toledo |
| Third Crusade | Tercera Cruzada |
| Third dynasty of Egypt | Dinastía III de Egipto |
| Third Dynasty of Ur | Renacimiento sumerio |
| Third Epistle of John | Tercera epístola de Juan |
| Third gender | Tercer sexo |
| Third Girl | La tercera muchacha |
| Third Intermediate Period of Egypt | Tercer periodo intermedio de Egipto |
| Third Italian War of Independence | Guerra de las Siete Semanas |
| Third Macedonian War | Guerras Macedónicas |
| Third Mithridatic War | Tercera Guerra Mitridática |
| Third normal form | Tercera forma normal |
| third party | tercera persona |
| third person | tercera persona |
| Third Punic War | Tercera Guerra Púnica |
| Third Reich | tercer Reich |
| Third Republic | Tercera República Francesa |
| Third Rome | Nueva Roma |
| Third Servile War | Tercera Guerra Servil |
| third stomach | tercer estómago |
| Third Temple | Tercer templo de Jerusalén |
| third time's a charm | a la tercera va la vencida |
| Third Way | Tercera Vía |
| Third World | Tercer Mundo |
| third-class | de tercera categoría |
| third-degree | de tercer grado |
| Third-generation programming language | Lenguaje de Tercera Generación |
| Third-party developer | Third-party |
| third-rate | de poca calidad |
| Third-rate film | Brassica rapa |
| Third-worldism | Tercermundismo |
| thirdly | en tercer lugar |
| thirds | terciar |
| thirst | sed |
