| Ondansétron | Ondansetron |
| Ondarroa | Ondarroa |
| onde | wave |
| Onde acoustique | Acoustic wave |
| Onde acoustique de surface | Surface acoustic wave |
| onde courte | shortwave |
| Onde dans les plasmas ionique | Ion plasma wave |
| Onde de Bloch | Bloch wave |
| onde de choc | shock wave |
| Onde de choc ionisante | Ionizing shock wave |
| Onde de derive | Drift wave |
| Onde de gravite | Gravity waves |
| Onde de Kelvin | Kelvin wave |
| Onde de plasma | Waves in plasmas |
| Onde de plasmas | Plasma wave |
| Onde de Rossby | Rossby wave |
| onde de shock | bow shock |
| onde d’Alfvén | Alfvén wave |
| Onde electromagnetique | Electromagnetic waves |
| Onde electrostatique | Electrostatic waves |
| onde gravitationnelle | gravitational wave |
| Onde hydromagnetique | Hydromagnetic waves |
| Onde hydromagnétique | Hydromagnetic wave |
| Onde millimetrique | Millimeter waves |
| Onde millimétrique | Millimeter wave |
| Onde mécanique progressive | Mechanical wave |
| Onde orographique | Orographic lift |
| onde sonore | sound wave |
| onde stationnaire | standing wave |
| Onde submillimetrique | Submillimeter waves |
| Onde sur une corde vibrante | Vibrating string |
| Onde ultracourte | Ultra short wave |
| onde à hyperfréquences | microwave |
| onde électromagnétique | electromagnetic wave |
| Onde électrostatique | Electrostatic wave |
| ondelette | wavelet |
| ondes courtes | shortwave |
| Ondes décamétriques | Golf |
| Ondes kilométriques | Golf |
| Ondes longues | Golf |
| Ondes Martenot | Ondes Martenot |
| Ondin | Nix |
| Ondinisme | Urolagnia |
| Ondol | Ondol |
| ondoyer | wave |
| ondulation | wave |
| ondulatoire | wavelike |
| onduler | wave |
| onduleux | undulating |
| ondulé | spiraled |
| Ondárroa | Ondárroa |
| ondé | tabby |
| One | One Railway |
| One Canada Square | One Canada Square |
| One Day In Your Life | One Day in Your Life |
| One Laptop per Child | One Laptop per Child |
| One Piece | One Piece |
| One-day International | One-Day International |
| One-man-show | One person show |
| One-Pound Gospel | One-Pound Gospel |
| One-Two-Go Airlines | One-Two-GO Airlines |
| Onega | Onega |
| Oneida | Oneida |
| Oneille | Oneglia |
| Oneiroi | Oneiroi |
| ONEM | Labor Exchange |
| Oneonta | Oneonta |
| Onesti | Onesti |
| Oneworld | Oneworld |
| Oneşti | Oneşti |
| Onfroi de Hauteville | Humphrey of Hauteville |
| Onfroy Ier de Toron | Humphrey I of Toron |
| Onfroy II de Toron | Humphrey II of Toron |
| Onfroy IV de Toron | Humphrey IV of Toron |
| Ongaonga | Ongaonga |
| ongle | thumbnail |
| ongle d'orteil | toenail |
| ongle du pouce | thumbnail |
| onglet | tab |
| onguent | salve |
| onguent contre les brûlures | ointment for burns |
| ongulé | ungulate |
| Oni | Oni |
| Onibaba | The Hollow |
| onirique | dreamlike |
| Onkelos le Prosélyte | Onkelos |
| Online Computer Library Center | OCLC |
| Online public access catalog | OPAC |
| Online public access catalogue | OPAC |
| Onmyouza | Onmyo-Za |
| Onneiouts | Oneida tribe |
| Onnens | Onnens |
| Onoda Hirō | Hiroo Onoda |
| Onofre Marimón | Onofre Marimón |
| Onomastique | Onomastics |
| onomatopée | onomatopoeia |
| Ononis | Ononis |
| Onotoa | Onotoa |
| Ons Heemecht | Ons Hémécht |
| Onsen | Onsen |
| Onsernone | Onsernone |
