| one-arm bandit | máquina tragamonedas |
| one-armed | manco |
| one-armed bandit | máquina tragamonedas |
| One-child policy | Demografía de China |
| One-click hosting | Alojamiento inmediato |
| one-eyed | tuerto |
| One-form | Covector |
| one-night stand | aventura amorosa de una noche |
| One-parameter group | Grupo uniparamétrico |
| one-piece | de una pieza |
| One-Pound Gospel | One Pound Gospel |
| one-room apartment | estudio |
| one-sided | parcial |
| one-time | único |
| One-time pad | Libreta de un solo uso |
| One-time password | OTP |
| One-to-one and onto | Función biyectiva |
| one-way | de dirección única |
| One-way function | Funciones de un solo sentido |
| Oneesama | Onee-sama |
| Onega | Lago Onega |
| Onega River | Lago Onega |
| Oneglia | Oneglia |
| Oneida tribe | Oneida |
| Oneiroi | Oniros |
| Oneirology | Onironauta |
| Oneness Pentecostalism | Pentecostales del nombre de Jesucristo |
| onerous | oneroso |
| onerousness | ajobo |
| Ones complement | Complemento a uno |
| oneself | se |
| Onesimus | Onésimo |
| onetime | antiguo |
| OneTouch Premier League | FA Premier League |
| Oneworld | Oneworld |
| Onex | Onex |
| Oneşti | Oneşti |
| Ongaonga | Urtica ferox |
| ongoing | continuo |
| Ongota language | Idioma ongota |
| Oni | Oni |
| Onibaba | Sangre en la piscina |
| onion | cebolla |
| Onion ring | Aros de cebolla |
| onionskin | papel cebolla |
| Online advertising | Marketing en Internet |
| Online analytical processing | OLAP |
| Online auction business model | Subasta electrónica |
| Online banking | Banca online |
| Online game | Juegos en línea |
| online help | ayuda en pantalla |
| Online magazine | Ezine |
| Online OsiriX Documentation | Documentación en línea de OsiriX |
| Online poker | Póquer online |
| onlooker | espectadora |
| only | salvo que |
