As you learned in Lesson 10, 7th chords are a major triad chord with the addition of a 7th note. In a dominant 7th chord, the 7th note is flattened by dropping the note a 1/2 step; however, there are several other possible 7th chord combinations.
Minor 7th Chords
Minor 7th chords are simply a minor chord with an added minor 7th note. The 11minor” in the chord name refers to the minor 3rd in a basic minor triad, which help to make up the minor 7th chord. The “7th” in a minor 7th chord refers to the 7th tone in the scale of this chord, which is also flattened to be played as a minor tone, just like in the dominant 7th chords found in Lesson 10. Common notations for minor 7th chords are m7, min7, and -7 (e.g. Cm7, Cmin7, C-7).