operating system vs software

operating system and software both are nouns.

Word	Noun	Adjective	Verb	Adverb
operating system	Yes	No	No	No
software	Yes	No	No	No

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

operating system: (computer science) software that controls the execution of computer programs and may provide various services
software: (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 operating system include computer software, package, software package, software program, software system.

operating system (noun)	software (noun)
(computer science) software that controls the execution of computer programs and may provide various services	(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