A system software component that is external to the operating system kernel. If the phrase is used to refer to the operating system itself, it is redundant because an operating system "is" software.

An operating system is the essential software that's needed to run your computer's suite of software. Everything from video ...

Just about every piece of technology has some form of an operating system – desktops, laptops, mobile phones, and servers, to name just a few. The Merriam-Webster definition of an operating system?