There are 16 words that start with 'doubt'.
| doubt | doubts |
| doubted | doubter |
| doubters | doubtful |
| doubting | doubtable |
| doubtless | doubtfully |
| doubtingly | doubtlessly |
| doubtfulness | doubtlessness |
| doubtfulnesses | doubtlessnesses |
Note: These 16 words that start with 'doubt' are found from the USA & Canada version of the tournament Scrabble word list.