There are 14 12-letter words that start with 'eff'.
| effectuality | effectuating | effectuation |
| effeminacies | effervescent | effervescing |
| effetenesses | efficacities | efficiencies |
| efflorescent | efflorescing | effortlessly |
| effronteries | effusiveness | |
Note: These 14 12-letter words that start with 'eff' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with effe, effl, effu, effi, effa, effo, effr, effs.
4-letter words start with 'eff' (1)