18-letter words containing e, s, t, a
- yerkes observatory — an astronomical observatory located in Williams Bay, Wisconsin, affiliated with the University of Chicago, and having a 40-inch (102-cm) refracting telescope, the largest refractor in the world.
- young conservative — a member of the youth section of the United Kingdom Conservative Party
- yves saint laurent — Louis Stephen [lwee ste-fen] /lwi stɛˈfɛn/ (Show IPA), 1882–1973, prime minister of Canada 1948–57.
- zone of saturation — the ground below the water table