Dominant 7th (7)

Root Position

Prove it — just do the practice exercise.
G7 Root Position
G (R)B (3)D (5)F (♭7)
The Dominant 7 creates tension — it wants to resolve.

Root
Major 3rd — 4 semitones
5th — 7 semitones
Minor 7th — 10 semitones

Example: G7 = G + B + D + F

Difference from Maj7: The seventh is one semitone lower (10 instead of 11 semitones).