X chromosome X ray X-OR circuit X-SCID X-linked X-linked SCID X-linked dominant inheritance X-linked gene X-linked recessive inheritance X-radiation X-ray X-ray diffraction X-ray film X-ray machine X-ray photograph X-ray photography X-ray picture X-ray therapy X-ray tube X-raying X-tail XC XI XII XIII XIV XIX XL XOR circuit XOR gate XT XTC XV XVI XVII XVIII XX XXI XXII XXIII XXIV XXIX XXV XXVI XXVII XXVIII XXX XXY XXY-syndrome XY XYY Xanax Xanthium Xanthomonas Xanthophyceae Xanthorrhoeaceae Xanthorroea Xanthosoma Xanthosoma atrovirens Xanthosoma sagittifolium Xantusiidae Xe Xenarthra Xenicidae Xenicus Xenicus gilviventris Xenopodidae Xenopus Xenopus laevis Xenorhyncus Xenorhyncus asiaticus Xenosauridae Xenosaurus Xeranthemum annuum Xerobates Xerophyllum Xerophyllum tenax Xerox machine Xestobium rufovillosum Xhosa Xhosa language Ximenesia encelioides Xiphias Xiphias gladius Xiphiidae Xiphosura Xiphosurus polyphemus Xishuangbanna Dai Xmas Xylaria Xylaria mali Xylaria polymorpha Xylariaceae Xylocaine Xylocopa Xylomelum Xylomelum pyriforme Xylopia Xylopia aethiopica Xylosma congestum Xyphophorus Xyphophorus helleri Xyridaceae Xyridales Xyris Xyris operculata x-axis x-ray x64 x86 xanthate xanthelasma xanthemia xanthic acid xanthine xanthoma xanthoma disseminatum xanthoma multiplex xanthomatosis xanthomonad xanthophyl xanthophyll xanthopsia xanthosis xanthous xc xci xcii xciii xciv xcl xcv xcvi xcvii xcviii xenogeneic xenogenesis xenograft xenolith xenon xenophobia xenophobic xenotime xenotransplant xenotransplantation xeranthemum xeric xeroderma xeroderma pigmentosum xerodermia xerographic xerographic copier xerographic printer xerography xeroma xerophile xerophilous plant xerophthalmia xerophthalmus xerophyte xerophytic xerophytic plant xeroradiography xerostomia xerotes xerox xerox copy xi xii xiii xiphium iris xiphoid process xix xli xlii xliii xliv xlv xlvi xlvii xlviii xv xvi xx xxi xxii xxiii xxiv xxix xxviii xxx xxxi xxxii xxxiii xxxiv xxxv xxxvi xxxvii xxxviii xylem xylene xylol xylometer xylophone xylophonist xylose xylosma