The triad can be defined as a chord made up of three tones (notes) called chord factors. They make up the diatonic scale. A D-major triad (aka chord) is made up of the notes D, F-sharp, and A. Add a major third above the major triad i.e., the root chord. The new note (the letter C) is the major seventh of the chord. It lies at the interval of a major seventh above the root.
What is an interval in music?
What is an Interval in Music? An interval in music is defined as a distance in pitch between any two notes. The larger the interval between two notes, then the greater the difference in pitch between the notes. And vice versa, the smaller the interval between two notes then the smaller the pitch between the notes. SOURCE: Wikipedia