washer (noun): a native English word of uncertain origin. Many people assume it is connected to the verb wash because washers are placed in hoses and faucets to prevent liquids from “washing” or spilling out. Nevertheless, no clear historical evidence exists to link the words washer and wash. In calculus volumes of revolution of certain solids may be calculated using the washer method, which relies on summing up the volumes of thin elements that look like washers.

wave (noun): a native English word, from the Indo-European root wegh- “to go, to transport.” A wave is literally water “going somewhere.” The development of wave, the noun, was influenced by wave, the verb “to move a hand up and down”; the two words are actually from different Indo-European sources. In mathematics waves are typically represented by sinusoidal functions. [243]

weak (adjective): from the Old Norse adjective veikr “pliant, flexible,” which supplanted the cognate native English adjective wac. The Indo-European root is weik- “to bend, to wind.” In mathematics various abstract concepts may be modified by the adjective weak; some examples are weak compactness, weak completeness, weak convergence, and weak topology. [246]

wedge (noun): a native English word with cognates in other Germanic languages; probably from the Indo-European root wogw-ni- “plowshare, wedge.” In plane geometry an infinite wedge is any of the four regions created by two intersecting lines. In solid geometry an infinite wedge is any of the four regions created by two intersecting planes.