Guitar is one of musical instruments with ancient roots that is used in a wide variety of musical styles. Guitar as an instrument typically has six strings, but four strings, seven strings, eight strings, ten strings, elevenstrings, twelve strings, thirteen strings and eighteen strings guitars also exist.
Before the development of the electric guitar and the use of synthetic materials, a guitar was defined as being an instrument having "a long, fretted neck, flat wooden soundboard, ribs, and a flat back, most often with incurved sides".
Instruments similar to the guitar have been popular for at least 5,000 years. While today's classical guitar first appeared in Spain, it was itself a product of the long and complex history that saw a number of related guitar types developed and used across Europe. The roots of the guitar can be traced back thousands of years to an Indo-European origin in instruments, then known in central Asia and India.
For this reason the guitar itself is distantly related to instruments such as the tanbur and setar, and the Indian sitar. The oldest known iconographic representation of an instrument displaying all the essential features of a guitar being played is a 3,300 year old stone carving of a Hittite bard.
The modern word, guitar, was adopted into English from Spanish guitarra (German Gitarre, French Guitare), loaned from the medieval Andalusian Arabic qitara, itself derived from the Latin cithara, which in turn came from the earlier Greek word kithara, which is descended from the Old Persian word sihtar. Illustration from a Carolingian Psalter from the 9th century, showing a guitar-like plucked instrument.
The modern guitar is descended from the Roman cithara brought by the Romans to Hispania around 40 AD, and further adapted and developed with the arrival of the four-string oud, brought by the Moors after their conquest of the Iberian peninsula in the 8th century.
Elsewhere in Europe, the indigenous six-string Scandinavian lut (lute), had gained in popularity in areas of Viking incursions across the continent. Often depicted in carvings c. 800 AD, the Norse hero Gunther (also known as Gunnar), played a lute with his toes as he lay dying in a snake-pit, in the legend of Siegfried.
By 1200 AD, the four string "guitar" had evolved into two types: the guitarra morisca (Moorish guitar) which had a rounded back, wide fingerboard and several soundholes, and the guitarra latina (Latin guitar) which resembled the modern guitar with one soundhole and a narrower neck.
The Spanish vihuela or "viola da mano", a guitar-like instrument of the 15th and 16th centuries is, due to its similarities, is often considered an important influence in the development of the modern guitar. It had lute-style tuning and a guitar-like body. Its construction had as much in common with the modern guitar as with its contemporary four-course renaissance guitar.
The vihuela enjoyed only a short period of popularity; the last surviving publication of music for the instrument appeared in 1576. It is not clear whether it represented a transitional form or was simply a design that combined features of the Arabic oud and the European lute. In favor of the latter view, the reshaping of the vihuela into a guitar-like form can be seen as a strategy of differentiating the European lute visually from the Moorish oud.
Meanwhile, the five string renassance guitar and the baroque guitar enjoyed popularity, especially in Italy and France, and indeed, much of Europe from the 15th to the 18th centuries.
The Vinaccia family of luthiers is known for developing the mandolin, and may have built the oldest surviving six string guitar. Gaetano Vinaccia (1759 – after 1831) has his signature on the label of a guitar built in Naples, Italy for six strings with the date of 1779. This guitar has been examined and does not show tell-tale signs of modifications from a double-course guitar although fakes are known to exist of guitars and identifying labels from that period.
The dimensions of the modern classical guitar (also known as the Spanish guitar) were established by Antonio Torres Jurado (1817-1892), working in Seville in the 1850s. Torres and Louis Panormo of London (active 1820s-1840s) were both responsible for demonstrating the superiority of fan strutting over transverse table bracing.
Further Reading: Wikipedia