In the music theory of harmony, the root is a specific note that names and typifies a given chord. Chords are often spoken about in terms of their root, their quality, and their extensions. When a chord is named without reference to quality, it is assumed to be major—for example, a "C chord" refers to a C major triad, containing the notes C, E, and G. In a given harmonic context, the root of a chord need not be in the bass position, as chords may be inverted while retaining the same name, and therefore the same root.
In tertian harmonic theory, wherein chords can be considered stacks of third intervals (e.g. in common practice tonality), the root of a chord is the note on which the subsequent thirds are stacked. For instance, the root of a triad such as E Minor is E, independently of the vertical order in which the three notes (E, G and B) are presented. A triad can be in three possible positions, a "root position" with the root in the bass (i.e., with the root as the lowest note, thus E, G, B or E, B, G from lowest to highest notes), a first inversion, e.g. G, B, E or G, E, B (i.e., with the note which is a third interval above the root, G, as the lowest note) and a second inversion, e.g. B, E, G or B, G, E, in which the note that is a fifth interval above the root (B) is the lowest note.
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