What does the term "mediant" refer to in tonal music theory?

In tonal music theory, the term "mediant" specifically refers to the third scale degree of a diatonic scale. This degree plays a crucial role in establishing the harmonic function and structure of a piece of music. The mediant is positioned two steps above the tonic (the first scale degree) and is considered an important element in chord progressions, particularly because it helps in creating a sense of movement and emotional depth within the harmony.

For example, in the C major scale (C-D-E-F-G-A-B), E is the mediant. Understanding the mediant's function allows musicians and composers to explore a variety of harmonic relationships, since chords built on the mediant can provide contrasting colors and resolutions in a musical context. This concept is fundamental in both composition and analysis, making the mediant an integral part of tonal harmony.