- x
- x chromosome
- x ray
- xanax
- xanthate
- xanthelasma
- xanthemia
- xanthic acid
- xanthine
- xanthium
- xanthoma
- xanthoma disseminatum
- xanthoma multiplex
- xanthomatosis
- xanthomonad
- xanthomonas
- xanthophyceae
- xanthophyl
- xanthophyll
- xanthopsia
- xanthorrhoeaceae
- xanthorroea
- xanthosis
- xanthosoma
- xanthosoma atrovirens
- xanthosoma sagittifolium
- xanthous
- xantusiidae
- xavier
- x-axis
- xc
- xci
- xcii
- xciii
- xciv
- xcl
- xcv
- xcvi
- xcvii
- xcviii
- xe
- xenarthra
- xenicidae
- xenicus
- xenicus gilviventris
- xenogeneic
- xenogenesis
- xenograft
- xenolith
- xenon
- xenophanes
- xenophobia
- xenophobic
- xenophon
- xenopodidae
- xenopus
- xenopus laevis
- xenorhyncus
- xenorhyncus asiaticus
- xenosauridae
- xenosaurus
- xenotime
- xenotransplant
- xenotransplantation
- xeranthemum
- xeranthemum annuum
- xeric
- xerobates
- xeroderma
- xeroderma pigmentosum
- xerodermia
- xerographic
- xerographic copier
- xerographic printer
- xerography
- xeroma
- xerophile
- xerophilous plant
- xerophthalmia
- xerophthalmus
- xerophyllum
- xerophyllum tenax
- xerophyte
- xerophytic
- xerophytic plant
- xeroradiography
- xerostomia
- xerotes
- xerox
- xerox copy
- xerox machine
- xerxes i
- xerxes the great
- xestobium rufovillosum
- xhosa
- xi
- xian
- xii
- xiii
- ximenesia encelioides
- xinjiang
- xinjiang uighur autonomous region
- xiphias
- xiphias gladius
- xiphiidae
- xiphium iris
- xiphoid process
- xiphosura
- xiphosurus polyphemus
- xishuangbanna dai
- xiv
- xix
- xizang
- xl
- xli
- xlii
- xliii
- x-linked
- x-linked dominant inheritance
- x-linked gene
- x-linked recessive inheritance
- x-linked scid
- xliv
- xlv
- xlvi
- xlvii
- xlviii
- xmas
- xor circuit
- x-or circuit
- xor gate
- 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-scid
- xt
- xtc
- xv
- xvi
- xvii
- xviii
- xx
- xxi
- xxii
- xxiii
- xxiv
- xxix
- xxv
- xxvi
- xxvii
- xxviii
- xxx
- xxxi
- xxxii
- xxxiii
- xxxiv
- xxxv
- xxxvi
- xxxvii
- xxxviii
- xxy
- xxy-syndrome
- xy
- xylaria
- xylaria mali
- xylaria polymorpha
- xylariaceae
- xylem
- xylene
- xylocaine
- xylocopa
- xylol
- xylomelum
- xylomelum pyriforme
- xylophone
- xylophonist
- xylopia
- xylopia aethiopica
- xylose
- xylosma
- xylosma congestum
- xyphophorus
- xyphophorus helleri
- xyridaceae
- xyridales
- xyris
- xyris operculata
- xyy