18-letter words containing o, p, e, r
- wireless telephony — Now Rare. radiotelephony.
- women at point sur — a narrative poem (1927) by Robinson Jeffers.
- working hypothesis — See under hypothesis (def 1).
- x-ray spectrometer — a spectrometer using x-rays to activate the inner electrons of an atom in order to separate and identify the chemical constituents of a substance and their concentrations.
- x-ray spectrometry — the use of an x-ray spectrometer.