| XCE | X-chromosome controlling element |
|---|---|
| XD | x-ray diffraction |
| XDH | xanthine dehydrogenase |
| XDP | xanthine diphosphate; xeroderma pigmentosum |
| XDR | transducer |
| Xe | electric susceptibility; xenon |
| XECT | xenon-enhanced computed tomography |
| XEF | excess ejection fraction |
| XES | x-ray energy spectrometry |
| Xfb | cross-linked Gibrin |