Xi 166742 224966368 2008-07-11T06:07:15Z 24.85.164.36 {{wiktionarypar2|Ξ|ξ}} {{Table_Greekletters|letter=xi}} '''Xi''' (uppercase '''Ξ''', lowercase '''ξ''') is the 14th letter of the [[Greek alphabet]]. It is {{pronounced|ksi}} in [[Modern Greek]], and generally {{pronEng|ˈsaɪ}} (UK) or {{IPA|/ˈzaɪ/}} (US) in [[English language|English]]. In the system of [[Greek numerals]], it has a value of 60. In the system of [[Roman numerals]], it has a value of 11. The Xi is not to be confused with the letter [[Chi (letter)|Chi]], which takes the form of the Latin letter [[X]]. In ancient times, the [[Western Greek alphabet]] used it to represent {{IPA|/kʰ/}}, while it was used to represent /ks/ in other alphabets. As the alphabet was standardized, Xi was decided to be used for /ks/ and Chi for {{IPA|/kʰ/}}. While having no Latin derivative, the Xi was adopted into the [[early Cyrillic alphabet]], as the letter [[ksi]] ({{Unicode|Ѯ}}, {{Unicode|ѯ}}). The lower-case letter ξ is used as a symbol for [[Image:Xi alternate.png|frame|left|A joined variant of Ξ.]] *[[random variable]]s; *[[extent of reaction]] (a topic found most often in [[chemical engineering]] kinetics); *[[eigenvector]]s; *a parameter in a [[Pareto distribution#generalized Pareto distribution|generalized Pareto distribution]]; *the symmetric function equation of the [[Riemann zeta function]] in [[mathematics]], also known as the [[Riemann Xi function]]; *the [[damping factor]] in an [[RLC circuit]]; *a universal set in the [[set theory]]; *a number used in the error term of [[Newton–Cotes formulas]] that falls between ''a'' and ''b''; *one of the two different polypeptide chains of the human embryonic [[hemoglobin]] types Hb-Portland (ξ<sub>2</sub>γ<sub>2</sub>) and Hb-Gower I (ξ<sub>2</sub>ε<sub>2</sub>); *the [[correlation function (astronomy)|correlation function]] in [[astronomy]]; *frequency; *a small displacement in MHD [[plasma stability]] theory. *ξ・∀・) The upper-case letter Ξ is used as symbol for *The '[[Xi (particle)|cascade particles]]' in particle physics; *indicating "no change of state" in [[Z notation]]. [[Category:Greek letters]] [[als:Ξ]] [[ar:كشي (حرف إغريقي)]] [[arc:Ξ]] [[br:Xi (lizherenn)]] [[bg:Кси]] [[ca:Xi]] [[cy:Xi]] [[da:Xi (bogstav)]] [[de:Xi]] [[el:Ξι]] [[eo:Ksio]] [[es:Ξ]] [[eu:Xi]] [[fr:Xi]] [[ga:Xí]] [[gd:Xi]] [[gl:Xi]] [[ko:Ξ]] [[hr:Ksi]] [[id:Xi]] [[is:Xí]] [[it:Xi (lettera)]] [[he:קסי]] [[ka:ქსი (ასო)]] [[ht:Ξ]] [[ku:Xi]] [[la:Xi]] [[lt:Ksi (raidė)]] [[hu:Kszi]] [[ms:Xi]] [[nl:Xi (letter)]] [[ja:Ξ]] [[no:Xi]] [[nn:Xi]] [[nds:Xi]] [[pl:Ksi]] [[pt:Ξ]] [[ru:Кси (буква)]] [[sk:Ksí]] [[sl:Ksi]] [[sh:Ksi]] [[fi:Ksii]] [[sv:Xi]] [[th:ไซ (อักษรกรีก)]] [[tr:Ξ]] [[uk:Ксі (літера)]] [[zh:Ξ]]