There are 10 words that start with 'slen'.
| slender | slenderer | 
| slenderly | slenderest | 
| slenderize | slenderized | 
| slenderizes | slenderness | 
| slenderizing | slendernesses | 
Note: These 10 words that start with 'slen' are found from the USA & Canada version of the tournament Scrabble word list.