| X {letter} | :: The twenty-fourth letter of the German alphabet |
| Xänorphika {noun} | :: xaenorphica |
| Xanten {prop} {n} | :: Xanten (city) |
| Xanthin {n} | :: xanthine (group of alkaloids, including caffeine) |
| xanthochrom {adj} | :: xanthochromic |
| Xanthogenat {n} | :: xanthogenate, xanthate |
| Xaver {prop} | :: given name |
| x-beinig {adj} | :: knock-kneed |
| x-beliebig {adj} | :: indifferent |
| x-beliebig {adj} | :: any old |
| Xenia {prop} | :: given name |
| Xenobiologie {f} | :: xenobiology |
| Xenobiotikum {n} | :: xenobiotics |
| xenoblastisch {adj} | :: xenoblastic |
| Xenolith {m} | :: xenolith |
| Xenon {n} | :: xenon |
| Xenonfluorid {n} | :: xenon fluoride |
| Xenonhexafluorid {n} | :: xenon hexafluoride |
| Xenonverbindung {f} | :: xenon compound |
| xenophil {adj} | :: xenophilic |
| Xenophilie {f} | :: xenophilia |
| xenophob {adj} | :: xenophobic |
| Xenophobie {f} | :: xenophobia |
| xenophobisch {adj} | :: xenophobic |
| xenophontisch {adj} | :: Xenophontic |
| Xenotim {m} | :: xenotime |
| xerografisch {adj} | :: alternative form of xerographisch |
| xerographisch {adj} | :: xerographic |
| xeromorph {adj} | :: xeromorphic |
| xerophil {adj} | :: xerophilic, xerophilous |
| xerotherm {adj} | :: xerothermic |
| x-fach {adj} | :: n-tuple |
| x-förmig {adj} | :: X-shaped |
| Xi {n} | :: xi (Greek letter) |
| XNOR-Gatter {n} | :: XNOR gate, a logic gate performing a Boolean logic XNOR operation |
| XOR-Gatter {n} | :: XOR gate, a logic gate performing a Boolean logic XOR operation |
| xte {adj} | :: umpteenth, yet another; indicating a too high number of something already exist |
| XXO {n} | :: synonym of Tic-Tac-Toe |
| Xylem {n} | :: xylem |
| Xylenolorange {n} | :: xylenol orange |
| Xylitol {n} | :: xylitol (an alcohol) |
| Xylofon {n} | :: xylophone |
| xylografisch {adj} | :: alternative form of xylographisch |
| xylographisch {adj} | :: xylographic |
| Xylophon {n} | :: xylophone |
| Xylose {f} | :: xylose (wood sugar) |
| XYZ {prop} | :: used to replace a random personal name when describing a possible situation or when having forgotten the name in question |