A major triad is a chord with three notes *x,y,z* such that
*y* is 4 semitones higher than *x* and *z* is 3 semitones higher than *y*.

Alternatively, treating notes as integers, *(x,y,z)* is a major triad iff *(x,y,z)=(x,x+4,x+7)*.

Note that a major triad is composed of the first, the third, and the fifth sounds from a major scale.

Check out our definition of minor triads also explained on a virtual piano.