A three-note chord that is formed from any note of the scale, plus the note a third above it and the note a third above that. The lowest note is called the root (or root position), and the letter name of the root is used to identify the entire triad, e.g., the triad of C. In practice, the notes may be arranged in any order, although if the lowest note is no longer the root, the triad is said to be inverted. As either of the thirds can be either major or minor, four different types of triad are possible, as shown below. The most common are major triads (lower inter-val a major third) and minor triads (lower interval a minor third). It is important to note that these terms refer to the structure of the interval and not to key; major triads occur in minor keys, and vice-versa.