There are 16 9-letter words that start with 'eff'.
| effecters | effecting | effective | 
| effectors | effectual | efferents | 
| efficient | effluence | effluents | 
| effluvial | effluvium | effluxion | 
| effortful | effulgent | effulging | 
| effusions | ||
Note: These 16 9-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)