subroutine vs routine

subroutine and routine both are nouns.

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

As nouns, subroutine and routine are synonyms defined as:

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

Other synonyms of subroutine include function, procedure, subprogram.

subroutine (noun)	routine (noun)
a set sequence of steps, part of larger computer program	an unvarying or habitual method or procedure
	a set sequence of steps, part of larger computer program
	a short performance that is part of a longer program

subroutine (adjective)	routine (adjective)
	found in the ordinary course of events