There are 11 words that start with 'effic'.
| efficacy | efficient | 
| efficacies | efficacity | 
| efficiency | efficacious | 
| efficiently | efficacities | 
| efficiencies | efficaciously | 
| efficaciousness | |
Note: These 11 words that start with 'effic' are found from the USA & Canada version of the tournament Scrabble word list.