21-letter words containing o, p, e, r
- workers' compensation — a government-sponsored insurance system, funded by contributions from employers, for compensating employees for injury or occupational disease suffered in connection with their employment
- writ of habeas corpus — law: petition for hearing
- xeroderma pigmentosum — a rare inherited disease characterized by sensitivity to ultraviolet light, exposure resulting in lesions and tumors of the skin and eyes.
- xfree86 project, inc. — (operating system, graphics) A non-profit organisation that produces XFree86, a freely redistributable implementation of the X Window System that runs on Unix and Unix-like operating systems and OS/2. The XFree86 Project has traditionally focused on Intel x86 based platforms (hence the "86"), but the current release supports other platforms.
- yellow lady's-slipper — a showy orchid, Cypripedium calceolus, of eastern North America, having purple-tinged yellow flowers with an inflated lip petal.
- yellow-rumped warbler — a common North American wood warbler, Dendroica coronata, having yellow spots on the rump, crown, and sides, including a white-throated eastern subspecies (myrtle warbler) and a yellow-throated western subspecies (Audubon's warbler)