Good question. What would a minor chord with a major 7th added be called?   I guess a Dminor with an augmented 7th?

And I don't think a D7 would be the same as a D dominant 7th. In classical music a D dominant 7th starts on the dominant note of the scale (the 5th), so it would be an A C# E G.

Technically what we in popular music call a D7th (D F# A C) is, in classical terms, a G dominant 7th.

But for simplicity sake we just call it a D 7th.

Pretty confusing I know.