The string section is composed of bowed instruments belonging to the violin family. It normally consists of first and second violins, violas, cellos, and double basses. It is the most numerous group in the standard orchestra. In discussions of the instrumentation of a musical work, the phrase "the strings" or "and strings" is used to indicate a string section as just defined. An orchestra consisting solely of a string section is called a string orchestra. Smaller string sections are sometimes used in jazz, pop, and rock music and in the pit orchestras of musical theatre.
The most common seating arrangement in the 2000s is with first violins, second violins, violas, and cello sections arrayed clockwise around the conductor, with basses behind the cellos on the right. The first violins are led by the concertmaster (leader in the UK); each of the other string sections also has a principal player (principal second violin, principal viola, principal cello, and principal bass) who play the orchestral solos for the section, lead entrances and, in some cases, determine the bowings for the section (the concertmaster/leader may set the bowings for all strings, or just for the upper strings). The principal string players sit at the front of their section, closest to the conductor and on the row of performers which is closest to the audience.
In the 19th century it was standard to have the first and second violins on opposite sides (violin I, cello, viola, violin II), rendering obvious the crossing of their parts in, for example, the opening of the finale to Tchaikovsky's Sixth Symphony.
If space or numbers are limited, cellos and basses can be put in the middle, violins and violas on the left (thus facing the audience) and winds to the right; this is the usual arrangement in orchestra pits. The seating may also be specified by the composer, as in Béla Bartók's Music for Strings, Percussion and Celesta, which uses antiphonal string sections, one on each side of the stage.