@Suiseiseki >An Operating System is a *system* of software that allows you to *operate* a computer.
that's a lamer definition. I'm a system programmer, I professionally work with systems for whole life. and OS is the software that works with hardware, CPU scheduling, processes and provides API (system calls) for user layer. but you don't know such things as kernel level/user level, system calls, etc. and I know because I wrote drivers and so on.
so OS is the kernel, exactly. not anything else. Windoze also has its own kernel, it's bloated and buggy but it also has it's API. and I worked with different OSes and wrote system software.
and what you call "OS" it's a user level toys, it's really named ditribution. Linux distribution is kernel, some package utility (not all distributions have packets, though, but the most), base toolchain used to build up kernel and libc and a set of user layer software. on Linux GNU can present in user layer. but they have their own kenel Hurd. I really haven't dealt with it so cannot say much about it. but it exists and such system is usually GNU/Hurd but it may contain non-GNU user layer too, I suppose. nobody is binded to use GNU as a software of his choice, there're many other vatiants.
so your knowledge is limited and you spread disinformation.
so if the Linux kernel is used the operating system is Linux. well, that's simple. then next. GNU is some user space software. but you can build Linux based distributive with any software you like. not necessarily GNU. on my distributive (I build it from sources, myself) from GNU I have only compiler gcc and a couple of utils: binutils and maybe some little utils, I can't say becsuse they're a few. the rest 90% of user layer software is not GNU. I use musl as c library. so the software is not "GNU/Linux" or whatever, or you should write all developers in like Linux/musl/i3/whatever.../GNU. because GNU is just a part of it all, and not that much. and yes, I can use different compilers, gcc is needed for kernel. but it can be bullt by other compilers too. so it's easily possible to create Linux distribution without GNU at all. just a note.
I'm a programmer with over 30 years of writing in C. and I know what I say very well.