There are 15 words that start with 'proton'.
| proton | protons |
| protonic | protonate |
| protonema | protonated |
| protonates | protonemal |
| protonating | protonation |
| protonemata | protonotary |
| protonations | protonematal |
| protonotaries | |
Note: These 15 words that start with 'proton' are found from the USA & Canada version of the tournament Scrabble word list.