Minor Seventh (m7)

Root + minor third + minor seventh

Prove it — just do the practice exercise.
Cm7 Shell Voicing
C (R)Eb (♭3)Bb (♭7)
An m7 shell voicing consists of 3 notes:

Root
Minor 3rd — 3 semitones above the root
Minor 7th — 10 semitones above the root

Example: Cm7 = C + Eb + Bb

The difference from Dom7: the third is one semitone lower.