Long Answer: An operating system is a set of tools or software that you install on your computer or device and create a base system that allows you to extend its functionality by installing additional applications. In other words, an operating system is the minimum environment necessary to make your computer or device usable, then Linux is not an operating system because Linux by itself does not make your computer usable, in fact if you grab the Linux source code and compile it you will not get any practical use because the first thing you need is a boot loader (GRUB the most used is part of the GNU project), second an initialization system like systemd that take care of the initialization process (drivers, devices, file system, services) and finally the user tools: bash, ls, dir, top, find, grep (part of the GNU project) so what is Linux? Linux is a kernel, a kernel is a very important component of any operating system that interacts with the computer hardware (manages memory, processes, interrupts, devices, …), interact with the file system and with the user land, which is the correct name? GNU/Linux, see What’s in a Name? for more details.