Third (chord)

In a chord, the third factor is the note three scale degrees above the root. For instance, in a C major triad, E is the third factor.
When the third is the bass note of the triad or seventh chord, the chord is in first inversion.

Use

Conventionally, the third is third in importance to the root and fifth, with the third in all primary triads being either major or minor. In jazz chords and theory, the third is required due to it determining chord quality.
The third in both major and augmented chords is major and the third in both minor and diminished chords is minor.