The modern classical guitar, sometimes called Spanish guitar, is an acoustical wooden instrument that commonly employs nylon strings, as opposed to the metal strings in acoustic an electric guitars. The traditional classical guitar is merely one member of the guitar family, which includes instruments of different size and construction (such as flamenco guitars, tenor, baritone, and bass guitars, metal stringed guitars, etc).
The term 'modern' is sometimes applied to the Spanish guitar in order to distinguish it from the multiple older forms of the guitar, which includes instruments from the baroque and romantic period. Since the late 18th century (when the sixth string was added) the guitar progressively gained reputation as a solo instrument, but it was late 19th century Spanish luthier Antonio Torres Jurado who established the modern classical guitar design. Musicians such as Segovia and Tárrega helped popularize this version of the instrument, and eventually the previous designs fell away.
The guitar never achieved the status of the piano or the violin in the romantic academic music world. However, a good number of respected composers wrote for the instrument and regarded it in a high esteem: Berlioz studied the instrument, Schubert and Paganini wrote for it, and even Beethoven had words of praise for it. In the 20th century, with Tarrega and Segovia's legacy, the guitar consolidated as an academic instrument.