In mathematics, x is commonly used as the name for an independent variable or unknown value. While it is widely believed that the usage of x to represent an independent or unknown variable can be traced back to the Arabic word šay' شيء = “thing”, there are no sources to support this claim. Modern tradition of using x to represent unknowns was started by Rene Descartes in his La geometrie (1637).
It may also be used to signify the multiplication operation when a more appropriate glyph is unavailable. In mathematics, an "italicized x" is often used to avoid potential confusion with the multiplication symbol.
Other non-mathematical uses include:
- As a result of its use in algebra, X is often used to represent unknowns in other circumstances (e.g. Person X, Place X, etc.; see also Malcolm X).
- X-rays are so called because their discoverer did not know what they were.
- X has been used as a namesake for a generation of humans: Generation X, commonly abbreviated to Gen X. It is the generation born after the baby boom ended, ranging from 1961 to 1981.
- X is also used for referring to 'the end of conversation'.
- X is used by the illiterate in lieu of a signature and indicates a signature line on forms.
- In cartoons, a dead character's eyes are often drawn as Xs.
- X is commonly used as a generic mark (selecting an item on a form, indicating a location on a map, etc.).
- A typographic approximation of the multiplication sign × (especially, lowercase Roman "x"). Note that in any font the glyph of "x" is not exactly the same as one of the multiplication sign.
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Famous quotes containing the word usage:
“Pythagoras, Locke, Socratesbut pages
Might be filled up, as vainly as before,
With the sad usage of all sorts of sages,
Who in his life-time, each was deemed a bore!
The loftiest minds outrun their tardy ages.”
—George Gordon Noel Byron (17881824)