Thom Holwerda on OSNews has a few choice words for those who would argue against Android being a Linux distribution. As much respect as I have for Thom and OSNews, I have to disagree with him on this point. Android may be built around a fork of the Linux kernel, but it is distributed in an ecosystem quite alien to your standard Linux distro.
Thom's point is that Linux, not specifically addressing GNU/Linux, is a kernel, the core of an operating system that allows other processes to access the hardware. Without the kernel, there is no computer, so building an operating system around a kernel makes sense. The term "GNU/Linux" addresses the combination of userland programs (like a shell and command line tools) and desktop environments with the Linux kernel, building what we call the Linux distros. Ubuntu, Fedora, Slackware, and every other Linux distro are combinations of desktop environments built on top of their own fork of the Linux kernel, this is what creates an operating system. It takes both to make a computer run.