18-letter words containing h, e, l, p, s, y
- september holidays — a period of time in September when people do not have to go to school, college or work
- sling psychrometer — a psychrometer so designed that the wet-bulb thermometer can be ventilated, to expedite evaporation, by whirling in the air.
- sodium hyposulfite — sodium thiosulfate.
- spectroheliography — the process of obtaining an image of the sun in light of a particular wavelength, such as calcium or hydrogen, showing the distribution of the element over the surface and in the solar atmosphere, using a spectroheliograph
- spherical geometry — the branch of geometry that deals with figures on spherical surfaces.
- spotted flycatcher — a European woodland songbird, Muscicapa striata, with a greyish-brown streaked plumage: family Muscicapidae (Old World flycatchers)
- the encyclopedists — the writers of the French Encyclopedia (1751-72) edited by Diderot and d'Alembert, which contained the advanced ideas of the period
- up to the eyeballs — You use up to the eyeballs to emphasize that someone is in an undesirable state to a very great degree.
- whispering gallery — a space or gallery beneath a dome or broad arch in which low sounds produced at any of certain points are clearly audible at certain other distant points.
- white-spotted hyla — a type of tree frog (H. leucophyllata) of tropical America
- wireless telephony — Now Rare. radiotelephony.