GNU/Linux
The version of GNU which is widely used [today] called Linux, it is [basically] the GNU system, developed by the GNU Project. Linux is the program in the system that allocates the [machine]'s resources to the other programs that you run. It is an essential part of an operating system and can only function as part of a complete operating system. Linux is normally used in combination with the GNU operating system (GNU/Linux). Linux distributions are actually distributions of GNU/Linux.
Dude 1: "Hey [man], I'm running this [new] OS called Linux, works like a charm!" Dude 2: "I'd just like to interject for a moment. What you'[re] referring to as Linux, is in fact, GNU/Linux, or as I've recently taken to calling it, GNU plus Linux. Linux is not an operating system unto itself, but rather another [free] component of a fully functioning GNU system made useful by the GNU corelibs, [shell] utilities and vital system components comprising a full OS as defined by POSIX. Many computer users run a modified version of the GNU system every [day], without realizing it. Through a peculiar turn of events, the version of GNU which is widely used [today] is often called Linux, and many of its users are not aware that it is basically the GNU system, developed by the GNU Project. There really is a Linux, and these [people] are using it, but it is just a part of the system they [use]. Linux is the kernel: the program in the system that allocates the machine's resources to the other programs that you run. The kernel is an essential part of an operating system, but [useless] by itself; it can only function in the context of a complete operating system. Linux is normally used in combination with the GNU operating system: the whole system is basically GNU with Linux added, or GNU/Linux. All the so-called Linux distributions are really distributions of GNU/Linux." Dude 1: "What is this I [don]'[t] even"
This definition is too long for this mug.