There are 17 words that start with 'firm'.
| firm | firms | firman |
| firmed | firmer | firmly |
| firmans | firmers | firmest |
| firming | firmness | firmware |
| firmament | firmwares | firmaments |
| firmnesses | firmamental | |
Note: These 17 words that start with 'firm' are found from the USA & Canada version of the tournament Scrabble word list.