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.