| X and Y bosons | Bozon X |
| X band | Pasmo X |
| X Japan | X Japan |
| X PixMap | XPM |
| X ray | Promieniowanie rentgenowskie |
| X rays | Promieniowanie rentgenowskie |
| X window manager | Menedżer okien |
| X Window System core protocol | Protokół X Window System |
| X-COM series | X-COM |
| X-convention | X system |
| X-linked agammaglobulinemia | Agammaglobulinemia |
| X-mas | Boże Narodzenie |
| X-Men | X-Men |
| X-plane | X-plane |
| X-radiation | Promieniowanie rentgenowskie |
| X-ray | Promieniowanie rentgenowskie |
| X-ray crystallography | Rentgenografia strukturalna |
| X-ray diffraction | Rentgenografia strukturalna |
| X-ray machine | RTG |
| X-ray photo | Radiografia |
| X-ray photography | Radiografia |
| X-ray picture | Rentgenogram |
| X-ray treatment | Radioterapia |
| X-ray unit | aparat rentgenowski |
| X-rays | Promieniowanie rentgenowskie |
| X-wing | X-wing |
| Xabi Alonso | Xabi Alonso |
| Xagħra | Xaghra |
| Xai-Xai | Xai-Xai |
| Xaignabouli | Prowincja Sayaboury |
| Xaignabouli Province | Sayaboury |
| Xaisomboun | Prowincja Saysomboun |
| Xalapa | Jalapa Enriques |
| Xanadu | Xanadu |
| Xanadu House | Xanadu |
| Xanana Gusmão | Xanana Gusmão |
| Xander Harris | Alexander Harris |
| Xandros | Xandros |
| Xanten | Xanten |
| Xanth | Xanth |
| Xanthi | Ksanthi |
| Xanthi Prefecture | Ksanthi |
| Xanthophyceae | Złotowiciowce |
| Xanthoria parietina | Złotorost ścienny |
| Xanthos | Ksantos |
| xanthous | żółtobrązowy |
| Xantusiidae | Jaszczurki nocne |
| Xaver | Ksawery |
| Xavi | Xavi |
| Xavier | Ksawery |
| Xawery Czernicki | Xawery Czernicki |
| XBill | XBill |
| Xbox | Xbox |
| Xcel Energy Center | Xcel Energy Center |
| XCF | XCF |
| XChat | XChat |
| XD-Picture Card | Karta pamięci xD |
| XDR DRAM | XDR |
| Xe | Ksenon |
| Xekong Province | Prowincja Xekong |
| Xen | Xen |
| Xenarthra | Szczerbaki |
| Xenia | Ksenia |
| Xenia of Saint Petersburg | Ksenia z Petersburga |
| xenial | gościnny |
| Xenix | Xenix |
| xeno- | kseno- |
| Xenoglossy | Glosolalia |
| Xenomorph | Ksenomorf |
| xenon | ksenon |
| Xenophanes | Ksenofanes |
| xenophile | ksenofil |
| xenophobia | ksenofobia |
| Xenophon | Ksenofont |
| Xenophon Zolotas | Xenophon Zolotas |
| Xenophontos monastery | Ksenofont |
| Xenu | Xenu |
| Xeon | Xeon |
| Xerces | Apache Xerces |
| Xeres | Sherry |
| Xero | Xero Demo Tape |
| XeroBank Browser | Torpark |
| Xerocomus | Podgrzybek |
| xerographic printer | kserograf |
| xerox | kserować |
