X ray (n.), X-ray (adj.)
X Window System interface
year—1967 and 1968 annual reports; 1967–68 activities in the field; 1958–1963 findings (i.e., across decades include the entire number); the 1940s and 1950s (no apostrophe).
zero-pressure—takes the hyphen (adj.)
Zip disk—initial cap, for the removable disks used in a Zip drive from Iomega. [12/02]
ZIP file—all caps, for a file containing one or more compressed files. [12/02]
