A major seventh is a type of chord in music that consists of four notes. It is formed by stacking a major triad, which includes the root, major third, and perfect fifth, with an additional note called the major seventh. This seventh note is seven scale degrees above the root note, creating a rich and harmonious sound. In the context of music theory, the major seventh chord is often notated as Cmaj7 for a C major seventh chord, which includes the notes C, E, G, and B. This chord is commonly used in various genres, including jazz and pop, to add depth and complexity to musical compositions.