The string section is the largest body of the standard orchestra and consists of bowed string instruments of the violin family. It normally comprises five sections: the first violins, the second violins, the violas, the cellos, and the double basses (or basses). In discussions of the instrumentation of a musical work, the phrase "and strings" is used to indicate a string section as just defined.
In music of the classical period, the cellos and double basses often play from the same music, their parts usually being notated on a single staff, with the bassist's written notes sounding one octave lower than written.
An orchestra consisting solely of a string section is called a string orchestra.
The term is also used to describe a group of bowed string instruments used in rock, pop, jazz and commercial music. In this context the size and composition of the string section is less standardised, and usually smaller, than a classical complement.
Seating arrangement 
The most common seating arrangement is with first violins, second violins, violas and cellos clockwise around the conductor, with basses behind the cellos on the right. 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.
The pair of string players who play from the same sheet of music on the stand in front of them is called a "desk".
The size of a string section may be expressed with a formula of the type (for example) 10-10-8-10-6, designating the number of first violins, second violins, violas, cellos, and basses. The numbers can vary widely; thus in a large orchestra they might be 14-14-12-12-10; the band orchestra in Darius Milhaud's La création du monde is 1-1-0-1-1. Mozart's masses and offertories written for the Salzburg cathedral routinely dispensed with violas, as did his dances. Leonard Bernstein also left out the violas in his West Side Story. Famous works without violins include the Second Serenade of Brahms and Stravinsky's Symphony of Psalms, as well as Andrew Lloyd Webber's Requiem and Philip Glass's opera Akhnaten.
- Grove Dictionary of Music and Musicians, online edition, article "Orchestra", section 6.
- Size of the String Section in Popular Music Recordings, F.G.J.Absil, 2010
- Stanley Sadie's Music Guide, p. 56 (Prentice-Hall 1986). Nicolas Slonimsky described the cellos-on-the-right arrangement as part of a 20th century "sea change" (Lectionary of Music, p. 342 (McGraw-Hill 1989).
- "Orchestra" in Encyclopedia Americana (1948).
- Gassner, "Dirigent und Ripienist" (Karlsruhe 1844). Rousseau's Dictionnaire de musique (1768), however, has a figure showing second violins facing the audience and firsts facing the singers, reflecting the concertmaster's former role as conductor.