21-letter words containing r, e, t, i, l
- well-ordering theorem — the theorem of set theory that every set can be made a well-ordered set.
- west university place — a city in SE Texas.
- wet collodion process — a photographic process, in common use in the mid-19th century, employing a glass photographic plate coated with iodized collodion and dipped in a silver nitrate solution immediately before use.
- whistling in the dark — If you say that someone is whistling in the dark, you mean that they are trying to remain brave and convince themselves that the situation is not as bad as it seems.
- white-knuckle paddler — an inexpert and timid canoeist.
- wildlife photographer — someone that specializes in taking photographs of wild animals, especially in their natural habitats, and plants
- william the conqueror — ("the Conqueror") 1027–87, duke of Normandy 1035–87; king of England 1066–87 (son of Robert I, duke of Normandy).
- wilson's storm petrel — a small petrel, Oceanites oceanicus, that breeds in the Southern Hemisphere but ranges into the North Atlantic and Pacific oceans.
- with a capital letter — (used to give emphasis to a statement)
- worth someone's while — worth someone's time, consideration, etc.; profitable in some way
- xilinx netlist format — (language, electronics) (XNF) A Hardware Description Language for electronic circuit design, developed by Xilinx, Inc..
- yellow-fever mosquito — a mosquito, Aedes aegypti, that transmits yellow fever and dengue.
- yellow-throated vireo — an olive-green vireo, Vireo flavifrons, of eastern North America, having a bright yellow throat and breast.