Common Words:
* Date
* Deal
* Debt
* Deep
* Deny
* Desk
* Dice
* Dirt
* Doze
* Draw
* Dull
* Dump
Less Common Words:
* Dace (a type of fish)
* Davy (a nickname for David)
* Dink (a small, insignificant thing)
* Dour (stern and gloomy)
* Drat (an exclamation of annoyance)
* Dunn (a shade of brown)
* Dyke (a ditch or embankment)
This is not an exhaustive list, and there are likely many more four-letter words that start with "d."