subroutine

[suhb-roo-teen] /ˈsʌb ruˌtin/
noun, Computers.
1.
an instruction sequence in a machine or assembly language program that can be prewritten and referred to as often as needed.
Compare procedure (def 4a).
Origin
1945-50; sub- + routine
British Dictionary definitions for subroutines

subroutine

/ˈsʌbruːˌtiːn/
noun
1.
a section of a computer program that is stored only once but can be used when required at several different points in the program, thus saving space Also called procedure