X : X, the twenty-fourth letter of the English alphabet, has three sounds; a compound nonvocal sound (that of ks), as in wax; a compound vocal sound (that of gz), as in example; and, at the beginning of a word, a simple vocal sound (that of z), as in xanthic. See Guide to Pronunciation, // 217, 270, 271.

Example:
What was a good X-men: evolution episode that reflected the ideas of racism?

Taxonomy
Window System, freedesktop, mailing lists, Foundation, xorg, Wiki, bugzilla, report bugs, developers, mirror, financial sponsorship, project, open source implementation, development work, conjunction, educational non-profit corporation, major release, security updates.

Defination from the web:
X Window System, a system-architecture neutral, network-transparent windowing and user interface standard.