| Uniformitarianism | Uniformismo |
| uniformity | uniformidad |
| uniformly | constante |
| uniformness | uniformidad |
| unify | unir |
| Unikont | Unikonta |
| unilateral | unilateral |
| unilateralism | unilateralismo |
| Unilever | Unilever |
| unillumined | ignaro |
| unimaginable | inimaginable |
| unimaginative | poco imaginativo |
| Unimmunized | Frágiles |
| Unimodular matrix | Matriz unimodular |
| unimpeachable | intachable |
| unimpeded | claro |
| unimportant | trivial |
| unimportntant | futil |
| unimpressed | no impresionado |
| unimpressive | poco impresionante |
| uninformed | inculto |
| uninhabitable | inhabitable |
| uninhabited | desocupado |
| uninhibited | sin inhibición |
| uninitiated | no iniciado |
| uninjured | ileso |
| uninspired | aburrido |
| uninspiring | aburrido |
| uninstall | desinstalar |
| uninsurable | no asegurable |
| uninsured | no asegurado |
| unintelligent | ininteligente |
| unintelligently | ininteligentemente |
| unintelligibility | ininteligibilidad |
| unintelligible | incomprensible |
| unintelligibly | ininteligiblemente |
| unintended | no |
| unintentional | involuntario |
| unintentionally | sin querer |
| uninterested | desinteresado |
| uninterestedly | con apatía |
| uninteresting | aburrido |
| uninterrupted | continuo |
| uninterruptedly | continuamente |
| Uninterruptible power supply | Sistema de alimentación ininterrumpida |
| union | unión |
| Union Army | Ejército federal |
| Union between Sweden and Norway | Unión entre Suecia y Noruega |
| Union Centroamericana de Fútbol | Unión Centroamericana de Fútbol |
| Union County | Condado de Union |
| Union Cycliste Internationale | Unión Ciclista Internacional |
| Union de la gauche socialiste | Unión de Izquierda Socialista |
| Union Démocratique Bretonne | Unión Democrática Bretona |
| Union for a Popular Movement | Unión por un Movimiento Popular |
| Union for Democracy and Social Progress | Unión para la Democracia y el Progreso Social |
| Union for Europe of the Nations | Unión por la Europa de las Naciones |
| Union for French Democracy | Unión para la Democracia Francesa |
| Union for National Progress | Unión para el Progreso Nacional |
| Union for Peru | Unión por el Perú |
| Union Island | Unión de conjuntos |
| Union Jack | bandera del Reino Unido |
| Union of Arras | Unión de Arras |
| Union of Christian and Centre Democrats | Unión de los Demócratas Cristianos y de Centro |
| Union of Congolese Patriots | Unión de Patriotas Congoleños |
| Union of Democrats for the Republic | Unión de Demócratas por la República |
| Union of Liberals and Leftists | Unión de los Liberales y la Izquierda |
| Union of Russia and Belarus | Unión de Rusia y Bielorrusia |
| Union of South Africa | Unión Sudafricana |
| Union of South American Nations | Unión de Naciones Suramericanas |
| Union of Soviet Socialist Republics | URSS |
| Union of the Comoros | Comoras |
| Union of the Crowns | Unión de las Coronas |
| Union of the Democratic Centre | Unión de Centro Democrático |
| Union of Utrecht | Unión de Utrecht |
| Union Pacific | Unión Pacífico |
| Union Pacific Railroad | Union Pacific |
| Union Party | Partido de la Coalición Nacional |
| Union station | Hauptbahnhof |
| Union Territory | Territorios de la Unión |
| unionist | unionista |
| unionize | sindicar |
| unique | solo |
| Unique key | Clave primaria |
| uniqueness | peculiaridad |
| Uniramia | Uniramia |
