Terminology
Theorists are divided on whether a power chord can be considered a chord in the traditional sense, with some requiring a 'chord' to contain a minimum of three degrees of the scale. When the same interval is found in traditional and classical music, it would not usually be called a "chord", and may be considered to be a dyad or simply an interval. However, the term is accepted as a pop and rock music term, most strongly associated with the overdriven electric guitar styles of hard rock, heavy metal, punk rock, and similar genres. The use of the term "power chord" has, to some extent, spilled over into the vocabulary of other instrumentalists, such as keyboard and synthesizer players.
Power chords are most commonly notated 5 or (no 3). For example, "C5" or "C(no 3)" refer to playing the root (C) and fifth (G). These can be inverted, so that the G is played below the C (making an interval of a fourth). They can also be played with octave doublings of the root or fifth note, which will make a sound that is subjectively higher pitched with less power in the low frequencies, but still retains the character of a power chord.
Another notation is ind, designating the chord as 'indeterminate'. This refers to the fact that a power chord is neither major nor minor, as there is no third present. This gives the power chord a chameleon-like property; if played where a major chord might be expected, it can sound like a major chord, but when played where a minor chord might be expected, it will sound minor.
Although the power chord is associated with a distorted sound, most guitarists would consider that a power chord fingering can be called a power chord whether played through distortion or not.
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