21-letter words containing p, a, r, l, n
- supergranulation cell — one of a number of large convection cells in the photosphere and chromosphere of the sun, each having a diameter of 10,000–20,000 miles (16,000–32,000 km) and lasting longer than a day.
- supplementary benefit — (formerly) an extra amount of money that is paid to someone by the government, in addition to their normal income. Replaced by income support in 1988
- the central provinces — the Canadian provinces of Ontario and Quebec
- thermal decomposition — Thermal decomposition is the process in which a chemical species breaks down when its temperature is increased.
- thermal power station — a power station in which heat is converted into electricity
- to fall into the trap — If someone falls into the trap of doing something, they think or behave in a way which is not wise or sensible.
- topgallant forecastle — a partial weather deck on top of a forecastle superstructure; forecastle deck.
- topological invariant — a property of a topological space that is a property of every space related to the given space by a homeomorphism.
- trans-alaska pipeline — a pipeline system opened in 1977 that transports oil 800 miles (1300 km) across Alaska, from Prudhoe Bay on the North Slope S to Valdez harbor.
- traveling salesperson — a representative of a business firm who travels in an assigned territory soliciting orders for a company's services.
- ulster unionist party — a Northern Irish political party advocating the maintenance of union with the UK
- uncertainty principle — the principle of quantum mechanics, formulated by Heisenberg, that the accurate measurement of one of two related, observable quantities, as position and momentum or energy and time, produces uncertainties in the measurement of the other, such that the product of the uncertainties of both quantities is equal to or greater than h/ 2 π, where h equals Planck's constant.
- up close and personal — face to face, intimately
- west university place — a city in SE Texas.
- white-knuckle paddler — an inexpert and timid canoeist.
- wholesale price index — an indicator of price changes in the wholesale market