A six-string guitar has five musical-intervals between its consecutive strings. In standard tuning, the intervals are four perfect-fourths and one major-third, the comparatively irregular interval for the (G,B) pair. Consequently, standard tuning requires four chord-shapes for the major chords. There are separate chord-forms for chords having their root note on the third, fourth, fifth, and sixth strings.[41] Of course, a beginner learns guitar by learning notes and chords,[42] and irregularities make learning the guitar difficult[43]—even more difficult than learning the formation of plural nouns in German, according to Gary Marcus.[44] Nonetheless, most beginners use standard tuning.[45]
Guitars have been played since the Renaissance era, after descending from the ancient Greek instrument, the kithara. Or, at least, that's how the theory goes: the only real proof for this is the similarities between the Greek word and the Spanish word, quitarra. Early guitars often had four strings, evolving into the six-string version we know today in the late 1600s. Anton Stradivari, the famous violin-maker, also had a hand in making guitars. There's now only one Stradivarius guitar left in existence.