Original: 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".
Simplified: Types of guitars A guitar was described by Dr. Michael Kasha as an instrument that had "a long, fretted neck, flat wooden soundboard, ribs, and a flat back, most often with incurved sides".