What is GNU?
GNU's kernel isn't finished, so GNU is used with the kernel Linux. The combination of GNU and Linux is the GNU/Linux operating system, now used by millions.
Sometimes this combination is incorrectly called Linux. There are many variants or “distributions” of GNU/Linux.
We recommend the GNU/Linux distributions that are 100% free software; in other words, entirely freedom-respecting.
The name “GNU” is a recursive acronym for “GNU's Not Unix”; it is pronounced g-noo, as one syllable with no vowel sound between the g and the n.
A brief history of GNU