Each note of a triad has a name. The most important note is called the root. This, like the foundation of a house, is the vital note upon which the triad is built. It is also logically the note by which the triad is identified and named. To build a triad, above the root you place another note from the scale a third higher, and then a final note a fifth higher than the root.
So, for the triad of C major, you have:
Root (C) + Third (E) + Fifth (G)
A triad whose root note is C is thus called a triad of C.
Each note of the C major scale can be taken to be the root of a particular triad. Because there are seven notes in the scale, this means there are seven triads. So how do we distinguish between one triad and another? ...