| ondeugend | frolic |
| ondeugendheid | mischief |
| Ondicht | Prose |
| ondiep | superficial |
| ondiepte | shallows |
| onding | absurdity |
| Ondo | Ondo State |
| ondode | undead |
| ondoelmatig | inexpedient |
| ondoeltreffend | ineffective |
| ondoeltreffendheid | ineffectiveness |
| ondoordacht | silly |
| ondoordacht handelen | rush |
| ondoordachtheid | indiscretion |
| ondoordringbaar | impenetrable |
| ondoordringbaarheid | impenetrability |
| ondoorgrondelijk | abysmal |
| ondoorgrondelijkheid | impenetrability |
| ondoorlatend | impermeable |
| ondoorschijnend | opaque |
| ondoorzichtigheid | opaqueness |
| ondraaglijk | excruciating |
| ondrinkbaar | undrinkable |
| ondubbelzinnig | unambiguous |
| onduidelijk | obscure |
| onduidelijk uitspreken | slur |
| onduidelijkheid | ambiguity |
| onduldbaar | intolerable |
| onduleren | wave |
| One | One Railway |
| One Canada Square | One Canada Square |
| One Hour Photo | One Hour Photo |
| One Life to Live | One Life to Live |
| One Man Army and the Undead Quartet | One Man Army and the Undead Quartet |
| One Piece | One Piece |
| One Railway | One Railway |
| One Tree Hill | One Tree Hill |
| One-time code | One-time password |
| One-time-pad | One-time pad |
| One-Two-GO | One-Two-GO Airlines |
| onecht | false |
| onecht kind | bastard |
| onechte breuk | improper fraction |
| Onechte gaviaal | False gharial |
| Onechte karetschildpad | Loggerhead Sea Turtle |
| Onechte koraalslang | Anilius scytale |
| Onechte spitskopschildpad | Western Swamp Tortoise |
| Onechte waterrat | False Water Rat |
| oneconomisch | uneconomical |
| oneer | discredit |
| oneerbaar voorstel | improper suggestion |
| oneerbiedig | ill-mannered |
| oneerbiedigheid | disrespect |
| oneerlijk | unfair |
| oneerlijk verkregen | ill-gotten |
| oneerlijkheid | deceitfulness |
| oneetbaar | inedible |
| oneffen | uneven |
| oneffen maken | coarsen |
| Onega | Onega |
| Onegameer | Lake Onega |
| oneigenlijk | figurative |
