18-letter words containing y, e, i, s
- working hypothesis — See under hypothesis (def 1).
- yeast nucleic acid — RNA.
- yelloweye rockfish — a red rockfish, Sebastes ruberrimus, of waters along the Pacific coast of North America, having eyes that are yellow and possessed of strong, sawlike bony ridges on the head.
- 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.