A minor 7th chord is just like the major 7th only with the minor chord formation formula. Let’s take a look at what this looks like. A C minor scale is C D Eb F G Ab Bb C, Root = C, 3rd = Eb, 5th = G, and 7th = Bb. The formula for this chord construct is R-3b-5-7. Just like the major 7th chord, a standard triad is built out of the R-3b-5 and the 7th tone is added in.
Here are some of the common ways that these chords and notes will be referred to. Cm7, Dm7, Em7, Fm7, Gm7, Am7, Bm7, Cmin7, Dmin7, Emin7, Fmin7, Gmin7, Amin7, Bmin7.