A submediant chord is a musical chord built on the sixth degree of a scale. In the context of the major scale, this chord is typically a minor chord, while in the minor scale, it is often a major chord. For example, in the key of C major, the submediant chord is A minor, and in A minor, it is F major. Submediant chords play a significant role in harmony and can create a sense of movement or resolution in music. They are often used in chord progressions to add depth and variety, enhancing the emotional quality of a piece.