X

X is the twenty-fourth letter of the Latin alphabet. It is in the form of St Andrew's Cross.

/ks/ was in Ancient Greece written as Chi 'Χ' (Western Greek) or Xi 'Ξ' (Eastern Greek). In the end, Chi was standardized as /k_h/ (/x/ in Modern Greek) as well as Xi for /ks/. But the Etruscans took over X from older Western Greek, therefore, it stood for /ks/ in Etruscan and /ks/ and /gs/ [gz] in Latin. Only in Azeri, Uzbek and Tatar is X pronounced [kh]. Some scholars claim that Latin X is not identical with Greek X.

It is also controversial whether Psi, Chi (Khi) and Xi are Greek inventions or whether they are ultimately of Semitic origin.

X-ray represents the letter X in the NATO phonetic alphabet.

In context, X is also used as or in:

• The Roman numeral for ten.
• In elementary algebra, x commonly represents an unknown variable. Even though any letter can be used, x is the most common by far. This usage can be traced back to the Arabic word ?ay 'thing' which was spelled with an initial x in Old Spanish or (according to other sources) an abbreviation of Latin causa which was the translation of Arabic š.
• In a general sense, to represent the unknown or secret, as in project X and in the context of X rays, a form of electromagnetic radiation. Planet X is a hypothetical additional planet farther from the sun.
• Reference to sex, such as the X factor (this could of course refer to the unknown factor).
• Abbreviation for extra, such as XL for extra large size
• Abbreviation for Christ, as in Xmas (Christmas) and xtian (Christian).
• The stock symbol for United States Steel Corporation.
• Other abbreviations, such as Xtal (Crystal), reXn (reaction) and Xperimental (experimental).
• A represention for a cross in games like tic tac toe and in words like Xing (crossing), or to sign with a cross (often for illiteracy). Crossing something out with an X denotes elimination, prohibition or erasure.
• X Window System, a free graphical windowing system developed at MIT
• Slang for the drug MDMA, commonly called Ecstasy
• The X chromosome.
• Generation X
• X-rated, a US system for rating films for age groups. Also X was the old certificate in the UK for 18.
• Exact time in photographic flash synchronization
• A punk band (see X (band))
• X, a German film made in 1928
• X-Men, the superheros
• The X-files
• Several radio stations, such as 99X in Atlanta and 91X in Tijuana/San Diego
• The variable for reactance
• A kiss
• The pseudonym of the person who blew the whistle on the Watergate crisis
• A nickname for the École polytechnique
• A symbol for an alcoholic proof of 50; multiple Xes indicate multiples of 50
• The US Navy hull classification symbol for Submersible Craft
• Author of the X Article published in Foreign Affairs

Two-letter combinations starting with X:

• xa xb xc xd xe xf xg xh xi xj xk xl xm xn xo xp xq xr xs xt xu xv xw xx xy xz

Referenced By