There are 10 13-letter words that start with 'os'.
| oscillational | oscillographs |
| oscillography | oscilloscopes |
| oscilloscopic | ossifications |
| osteomalacias | osteomyelitis |
| osteoplasties | osteosarcomas |
Note: These 10 13-letter words that start with 'os' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with ost, osm, osc, oss, ose, osi, osn, osp, osa.
3-letter words start with 'os' (1)