- Onwards Adv.
- Oozily Adv.
- Opaquely Adv.
- Open Adj. Subst. Verb Adv.
- Openhanded Adj. Adv.
- Openhandedly Adv.
- Openheartedly Adv.
- Openly Adv.
- Operably Adv.
- Operatically Adv.
- Operationally Adv.
- Operatively Adv.
- Ophthalmologically Adv.
- Ophthalmoscopically Adv.
- Opinionatedly Adv.
- Opportunely Adv.
- Opportunistically Adv.
- Opposingly Adv.
- Opposite Adj. Subst. Präp. Adv.
- Oppositely Adv.
- Oppositionally Adv.
- Oppressively Adv.
- Opprobriously Adv.
- Optically Adv.
- Optimally Adv.
- Optimistically Adv.
- Optionally Adv.
- Opulently Adv.
- Or Konj. Subst. Adj. Präp. Adv.
- Oracularly Adv.
- Orally Adv.
- Oratorically Adv.
- Orbicularly Adv.
- Orbitally Adv.
- Orchestrally Adv.
- Orderly Adj. Subst. Adv.
- Ordinally Adv.
- Ordinarily Adv.
- Organically Adv.
- Organisationally Adv.
- Organismally Adv.
- Organizationally Adv.
- Organogenetically Adv.
- Organoleptically Adv.
- Organotropically Adv.
- Originally Adv.
- Ornamentally Adv.
- Ornately Adv.
- Ornithologically Adv.
- Orogenetically Adv.
- Orographically Adv.
- Orthodoxically Adv.
- Orthogenetically Adv.
- Orthogonally Adv.
- Orthographically Adv.
- Orthopedically Adv.
- Oscillographically Adv.
- Oscilloscopically Adv.
- Osmotically Adv.
- Osseously Adv.