Xi (letter)

Summary

Xi (/z/ ZY or /(k)s/ (K)SY;[1][2] uppercase Ξ, lowercase ξ; Greek: ξι) is the fourteenth letter of the Greek alphabet, representing the voiceless consonant cluster [ks]. Its name is pronounced [ksi] in Modern Greek. In the system of Greek numerals, it has a value of 60. Xi was derived from the Phoenician letter samekh .

Xi is distinct from the letter chi, which gave its form to the Latin letter X.

Greek

edit
 
A joined variant of Ξ (New Athena Unicode font)

Both in classical Ancient Greek and in Modern Greek, the letter Ξ represents the consonant cluster /ks/. In some archaic local variants of the Greek alphabet, this letter was missing. Instead, especially in the dialects of most of the Greek mainland and Euboea, the cluster /ks/ was represented by Χ (which in classical Greek is chi, used for /kʰ/).

Because this variant of the Greek alphabet was used in Magna Graecia (the Greek colonies in Sicily and the southern part of the Italian peninsula), the Latin alphabet borrowed Χ rather than Ξ as the Latin letter that represented the /ks/ cluster that was also present in Latin.

Cyrillic

edit

The Xi was adopted into the early Cyrillic alphabet, as the letter ksi (Ѯ, ѯ).

Mathematics and science

edit

Uppercase

edit

The uppercase letter Ξ is used as a symbol in various contexts.

Pure mathematics

edit

Physics

edit

Other uses

edit

Lowercase

edit

The lowercase letter ξ is used as a symbol for:

Pure mathematics

edit

Physics and astronomy

edit

Other uses

edit

Other uses

edit
 
Ξ for E in a commercial logo
  •   Media related to Xi (letter) at Wikimedia Commons

Uppercase Ξ is used as an 'E' to stylise company names/logos like Razer (styled as RΛZΞR), Tesla (styled as TΞSLA), the presidential campaigns of Joe Biden (styled as BIDΞN), musician Banners (styled as BANNΞRS), and in South Korean boy group ZE:A's newest logo (styled as "ZΞA") (Compare: Heavy Metal umlaut; Faux Cyrillic)

Unicode

edit

Unicode Code Charts: Greek and Coptic (Range: 0370-03FF)

  • U+039E Ξ GREEK CAPITAL LETTER XI (Ξ) (\Xi in TeX)
  • U+03BE ξ GREEK SMALL LETTER XI (ξ) (\xi in TeX)
  • U+2C9C COPTIC CAPITAL LETTER KSI
  • U+2C9D COPTIC SMALL LETTER KSI

The following characters are used only as mathematical symbols. Stylized Greek text should be encoded using the normal Greek letters, with markup and formatting to indicate text style:

  • U+1D6B5 𝚵 MATHEMATICAL BOLD CAPITAL XI
  • U+1D6CF 𝛏 MATHEMATICAL BOLD SMALL XI
  • U+1D6EF 𝛯 MATHEMATICAL ITALIC CAPITAL XI
  • U+1D709 𝜉 MATHEMATICAL ITALIC SMALL XI
  • U+1D729 𝜩 MATHEMATICAL BOLD ITALIC CAPITAL XI
  • U+1D743 𝝃 MATHEMATICAL BOLD ITALIC SMALL XI
  • U+1D763 𝝣 MATHEMATICAL SANS-SERIF BOLD CAPITAL XI
  • U+1D77D 𝝽 MATHEMATICAL SANS-SERIF BOLD SMALL XI
  • U+1D79D 𝞝 MATHEMATICAL SANS-SERIF BOLD ITALIC CAPITAL XI
  • U+1D7B7 𝞷 MATHEMATICAL SANS-SERIF BOLD ITALIC SMALL XI

References

edit
  1. ^ "xi". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  2. ^ "xi". New Oxford American Dictionary, 2nd Edition.
  3. ^ SPIE Optipedia article: "Spatial Frequency"
  4. ^ IUPAC Gold Book Entry: "Extent of Reaction" Archived June 29, 2012, at the Wayback Machine
  5. ^ Buckingham, John; Cooper, Caroline M.; Purchase, Rupert (18 November 2015). Natural Products Desk Reference. CRC Press. pp. 53–. ISBN 978-1-4398-7362-5.
  6. ^ Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names. 2014. pp. 1159–1160. ISBN 9780854041824. Retrieved 11 September 2017.
edit
  •   Media related to Xi (letter) at Wikimedia Commons