What term describes the minor key that shares the same key signature as a major key?

The term that describes the minor key sharing the same key signature as a major key is known as the relative minor. Each major key has a minor key that is directly related and shares the same key signature; this minor key is found a minor third below the tonic of the major key.

For example, in the key of C major, which has no sharps or flats, the relative minor is A minor, also having no sharps or flats in its key signature. This relationship is a fundamental aspect of music theory as it highlights how major and minor scales can coexist in a harmonious context due to their shared key signature.

Understanding the concept of the relative minor is essential for composers and musicians as it informs chord progressions, melodies, and the overall emotional character of musical pieces, helping to create contrast and depth in music.