There are 8 13-letter words that start with 'der'.
| deracinations | derealization | 
| deregulations | derepressions | 
| dermabrasions | dermatologies | 
| dermatologist | dermatophytes | 
Note: These 8 13-letter words that start with 'der' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with deri, dera, derm, dere, derr, dero, derb, derv, dern.
4-letter words start with 'der' (2)