routine vs subroutine

routine and subroutine both are nouns.

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

As nouns, routine and subroutine are synonyms defined as:

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

Other synonyms of routine include function, procedure, subprogram.

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

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