X -- X Window System -- [X Windows System]? -- X-Open? -- [X-Ray Crystallography]? -- [X-Ray Diffraction Pattern]? -- [X-Ray Spectrum]? -- [X-Ray Tube]? -- X-Rays? -- X-band Radar -- X-ray -- X-ray Astronomy -- X-ray crystallography -- XENIX? -- XHTML -- XML -- XOpen? -- XSL -- XTC -- Xe -- Xena -- Xenobiotic? -- Xenoglossy? -- Xenography? -- Xenolalia? -- Xenolith? -- Xenon -- Xenophobia -- Xenophon -- Xerox PARC -- Xetra DAX -- XfL -- Xiaoping Deng -- Xiemaisi -- Xingu -- Xslt -- Xudong Guan -- XudongGuan -- Xyplex? -- xmosaic?