A minor seventh chord is a four-note chord that consists of a root note, a minor third, a perfect fifth, and a minor seventh. For example, in a C minor seventh chord, the notes are C (root), E♭ (minor third), G (perfect fifth), and B♭ (minor seventh). This chord has a rich, warm sound and is commonly used in various music genres, including jazz and blues. The minor seventh chord can be notated as "Cm7" in chord symbols. It is often used to create a sense of tension and resolution in music, making it a popular choice for composers and songwriters. Understanding this chord can enhance one's ability to play and create music effectively.