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 music for a string section is not necessarily written in five parts; besides the variants discussed below, in classical orchestras the 'quintet' is often called a 'quartet', with basses and cellos playing together.