subprogram vs subroutine

subprogram and subroutine both are nouns.

Word	Noun	Adjective	Verb	Adverb
subprogram	Yes	No	No	No
subroutine	Yes	No	No	No

As nouns, subprogram and subroutine are synonyms defined as:

subprogram and subroutine: a set sequence of steps, part of larger computer program

Other synonyms of subprogram include function, procedure, routine.

subprogram (noun)	subroutine (noun)
a set sequence of steps, part of larger computer program	a set sequence of steps, part of larger computer program