There are 8 13-letter words that start with 'eff'.
| effectiveness | effectivities |
| effectualness | effectuations |
| effervescence | efficaciously |
| efflorescence | effortfulness |
Note: These 8 13-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)