subprogram vs software package

subprogram and software package both are nouns.

Word	Noun	Adjective	Verb	Adverb
subprogram	Yes	No	No	No
software package	Yes	No	No	No

As nouns, software package is a hypernym of subprogram; that is, software package is a word with a broader meaning than subprogram:

subprogram: a set sequence of steps, part of larger computer program
software package: (computer science) written programs or procedures or rules and associated documentation pertaining to the operation of a computer system and that are stored in read/write memory

Other hypernyms of subprogram include computer software, package, software, software program, software system.

subprogram (noun)	software package (noun)
a set sequence of steps, part of larger computer program	merchandise consisting of a computer program that is offered for sale
	(computer science) written programs or procedures or rules and associated documentation pertaining to the operation of a computer system and that are stored in read/write memory