X-brace—paired set of crossing sway braces. (See also brace, cross bracing, and sway brace.)
xonotlite—calcium silicate monohydrate (Ca6Si6O17(OH)2), a natural mineral that is readily synthesized at 302 to 662 F (150 to 350 C) under saturated steam pressure; a constituent of sand-lime masonry units.
X-ray diffraction—the diffraction of X-rays by substances having a regular arrangement of atoms; a phenomenon used to identify substances having such a structure.
X-ray emission spectroscopy—see X-ray fluorescence.
X-ray fluorescence—characteristic secondary radiation emitted by an element as a result of excitation by X-rays, used to yield chemical analysis of a sample.
X-ray radiograph—an X-ray film, plate, or paper that is placed at the image plane and is used for recording an X-ray image of the object being examined.