| Acronym | Meaning |
| XPS | X-ray Photoelectron Spectroscopy |
| XRCF | X-ray Calibration Facility |
| XRD | X-ray Diffraction Analysis |
| XRES | X-ray Emission Spectroscopy |
| XRF | X-ray Fluorescence |
| XRFA | X-ray Fluorescence Analysis |
| XRFS | X-ray Fluorescence Spectroscopy |
| XRMA | X-ray Microanalysis |
| XRMF | X-ray Microfluorescence |
| XRPD | X-ray Powder Diffraction |
| XRR | X-ray Reflectometry |
| XRS | X-Ray Spectroscopy |
| XSAD | X-ray Small Angle Diffraction |
| XSW | X-ray Standing Wave |
| XTEM | Cross-sectional Transmission Electron Microscopy |
| XTM | X-ray Tomographic Microscopy |
| XUV | Extreme Ultraviolet |
| Y-STR | Y Chromosome Short Tandem Repeat |
| YAC | Yeast Artificial Chromosome |
| YAEL | Yankee Atomic Environmental Laboratory |
| YAG | Yttrium Aluminum Garnet |
| YBCO | Yttrium Barium Copper Oxide |
| YFEGE | Yonei Free-electron-gas Exchange |
| YFP | Yellow Fluorescent Protein |
| YIG | Yttrium Iron Garnet |
| YLF | Yttrium Lithium Fluoride |
| YOS | Yttrium Orthosilicate |
| YSAG | Yttrium Scandium Aluminum Garnet |
| YSGG | Yttrium Scandium Gallium Garnet |
| YSZ | Yttria-stabilized Zirconia |
| ZAA | Zeeman Atomic Absorption |
| ZAAS | Zeeman Atomic Absorption Spectroscopy |
| ZAP | Zone Axis Pattern |
| ZASA | Zinc 5-aminosalicylate |
| ZBL | Ziegler, Biersack And Littmark |
| ZBLAN | Zirconium Barium Lanthanum Aluminum Sodium Fluoride |
| ZBLANP | Zirconium Barium Lanthanum Aluminum Sodium Lead Fluoride |
| ZCC | Zero Core Contribution (model For Photodetachment Calcns.) |
| ZCCSD | Z-vector Coupled Cluster (with) Single (and) Double Excitation |
| ZCLV | Zoned Constant Linear Velocity |
| ZDC | Zero-degree Calorimeter |
| ZDDO | Zero Diatomic Differential Overlap |
| ZDDP | Zinc Dialkyl Dithiophosphate |
| ZDO | Zero Differential Overlap |
| ZDT | Zero Ductility Temperature |
| ZECSY | Zero-quantum Coherence Correlation Spectroscopy |
| ZEKE | Zero Electron Kinetic Energy |
| ZERI | Zero Emissions Research Initiative |
| ZEV | Zero Emission Vehicle |
| ZF-NQR | Zero-field-nuclear Quadrupole Resonance |