How many notes make up a triad?

three tones

Triad, in music, a chord made up of three tones, called chord factors, of the diatonic scale: root, third, and fifth. The system of diatonic triads is the basis of tonal harmony in music. Triads built on the notes of the C major (and natural A minor) scale.

Explanation:

Triad, in music, a chord made up of three tones, called chord factors, of the diatonic scale: root, third, and fifth. The system of diatonic triads is the basis of tonal harmony in music. Triads built on the notes of the C major (and natural A minor) scale.