There are 15 words that start with 'pento'.
| pentode | pentose | 
| pentodes | pentomic | 
| pentosan | pentoses | 
| pentosans | pentoside | 
| pentoxide | pentosides | 
| pentoxides | pentobarbital | 
| pentobarbitals | pentobarbitone | 
| pentobarbitones | |
Note: These 15 words that start with 'pento' are found from the USA & Canada version of the tournament Scrabble word list.