There are 11 words that start with 'effer'.
| efferent | efferents |
| efferently | effervesce |
| effervesced | effervesces |
| effervescent | effervescing |
| effervescence | effervescences |
| effervescently | |
Note: These 11 words that start with 'effer' are found from the USA & Canada version of the tournament Scrabble word list.