# Upsilon

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Twentieth letter in the Greek alphabet

Not to be confused with the Greek letters [Epsilon](/source/Epsilon) or [γ](/source/%CE%93), the Latin letters [Upsilon](/source/Latin_upsilon), [Y](/source/Y), or [ʋ](/source/%C6%B2), or the Cyrillic letters [Ү](/source/%D2%AE) or [У](/source/%D0%A3). For other uses, see [Upsilon (disambiguation)](/source/Upsilon_(disambiguation)) and [Ypsilon (disambiguation)](/source/Ypsilon_(disambiguation)).

Greek alphabet Αα Alpha Νν Nu Ββ Beta Ξξ Xi Γγ Gamma Οο Omicron Δδ Delta Ππ Pi Εε Epsilon Ρρ Rho Ζζ Zeta Σσς Sigma Ηη Eta Ττ Tau Θθ Theta Υυ Upsilon Ιι Iota Φφ Phi Κκ Kappa Χχ Chi Λλ Lambda Ψψ Psi Μμ Mu Ωω Omega History Archaic local variants Ϝ Digamma Ͱ Heta Ϻ San Ϙ Koppa Ͷ Tsan Digamma Ͳ Sampi Ϸ Sho Diacritics and other symbols Diacritics ά ὰ ᾶ ἀ ἁ ᾱ ᾰ ϊ ᾳ σ̌ Ligatures ϗ ϛ Numerals (Attic) ϛ (6) ϟ (90) ϡ (900) Related topics Use as scientific symbols Orthography Romanization Cyrillization Category v t e

**Upsilon** ([US](/source/American_English): [/ˈʌpsɪlɒn, ˈ(j)uːp-, -lən/](https://en.wikipedia.org/wiki/Help:IPA/English), [UK](/source/British_English): [/(j)uːpˈsaɪlən, ˈʊpsɪlɒn/](https://en.wikipedia.org/wiki/Help:IPA/English) [ⓘ](https://en.wikipedia.org/wiki/File:LL-Q1860_(eng)-Flame,_not_lame-Upsilon.wav);[1][2][3][4][5][6] uppercase **Υ**, lowercase **υ**; [Greek](/source/Greek_language): [ύψιλον](https://en.wiktionary.org/wiki/%CF%8D%CF%88%CE%B9%CE%BB%CE%BF%CE%BD) *ýpsilon* [\[ˈipsilon\]](https://en.wikipedia.org/wiki/Help:IPA/Greek)) or **ypsilon** [/ɪp-/](https://en.wikipedia.org/wiki/Help:IPA/English)[1] is the twentieth letter of the [Greek alphabet](/source/Greek_alphabet). In the system of [Greek numerals](/source/Greek_numerals), Υʹ has a value of 400. It is derived from the [Phoenician](/source/Phoenician_alphabet) [waw](/source/Waw_(letter)) (𐤅).

The Greek alphabet on a [black figure](/source/Black_figure) vessel, with a V-shaped upsilon

## Etymology

The name of the letter was originally just υ (*y*, also called ὑ *hy*, hence *[hyoid](/source/Hyoid_bone)*, meaning 'shaped like the letter υ'), but the name changed to υ ψιλόν (=υ *psilon*, 'u-plain' or 'u-simple') to distinguish it from οι, which had come to have the same [y] pronunciation.[7]

## Pronunciation

In early [Attic Greek](/source/Attic_Greek) (6th century BCE), it was pronounced [[u](/source/Close_back_rounded_vowel)] (a [close back rounded vowel](/source/Close_back_rounded_vowel) like the English "long o͞o").[8][9] In [Classical Greek](/source/Ancient_Greek_language), it was pronounced [[y](/source/Close_front_rounded_vowel)] (a [close front rounded vowel](/source/Close_front_rounded_vowel)), at least until 1030.[10] In [Modern Greek](/source/Modern_Greek), it is pronounced [[i](/source/Close_front_unrounded_vowel)]; in the [digraphs](/source/Digraph_(orthography)) ⟨αυ⟩ and ⟨ευ⟩, as /f/ or /v/; and in the digraph ⟨ου⟩ as /u/. In ancient Greek, it occurred in both [long and short](/source/Ancient_Greek_phonology#Vowels) versions, but Modern Greek does not have a length distinction.

As an initial letter in Classical Greek, it always carried the [rough breathing](/source/Rough_breathing) (equivalent to *h*) as reflected in the many [Greek-derived English words](/source/English_words_of_Greek_origin), such as those that begin with *hyper-* and *hypo-*. This rough breathing was derived from an older pronunciation that used a [sibilant](/source/Sibilant_consonant) instead; this sibilant was not lost in Latin, giving rise to such cognates as *super-* (for *hyper-*) and *sub-* (for *hypo-*).

Upsilon participated as the second element in [falling diphthongs](/source/Falling_diphthong), which have subsequently developed in various ways.

## Correspondence with Latin Y

[Cyrillic **У**](/source/U_(Cyrillic)), [Latin **Y**](/source/Y) and Greek **Υ** (upsilon) and **ϒ** (hooked upsilon) in [FreeSerif](/source/GNU_FreeFont) – one of the few typefaces that distinguish between the Latin and the Greek form

The use of [Y](/source/Y) in Latin dates back to the first century BC. It was used to transcribe loanwords from Greek, so it was not a native sound of Latin and was usually pronounced /u/ or /i/. The latter pronunciation was the most common in the Classical period and was used mostly by uneducated people. The [Roman Emperor](/source/Roman_Emperor) [Claudius](/source/Claudius) proposed introducing a [new letter](/source/Claudian_letters) into the [Latin alphabet](/source/Latin_alphabet) to transcribe the so-called *sonus medius* (a short vowel before labial consonants), but in inscriptions, the new letter was sometimes used for Greek upsilon instead.

Four letters of the [Latin alphabet](/source/Latin_alphabet) arose from it: [V](/source/V), [Y](/source/Y) and, much later, [U](/source/U) and [W](/source/W). In the [Cyrillic script](/source/Cyrillic_script), the letters [U](/source/U_(Cyrillic)) (У, у) and *[izhitsa](/source/Izhitsa)* (Ѵ, ѵ) arose from it.

In some languages, including [German](/source/German_language) and [Portuguese](/source/Portuguese_language), the name *upsilon* (*Ypsilon* in German, *ípsilon* in Portuguese) is used to refer to the Latin letter **Y** as well as the Greek letter. In some other languages, the (Latin) Y is referred to as a "Greek I" (*i griega* in [Spanish](/source/Spanish_language), *i grec* in [French](/source/French_language) and [Romanian](/source/Romanian_language)), also noting its Greek origin.

## Usage

- In [particle physics](/source/Particle_physics) the capital Greek letter ϒ denotes an [Upsilon particle](/source/Upsilon_particle). Note that the symbol should always look like Υ {\displaystyle \,\Upsilon } in order to avoid confusion with a Latin Y denoting the [hypercharge](/source/Hypercharge). This may be done either with a font such as FreeSerif or with the dedicated Unicode character U+03D2 ϒ.

- Automobile manufacturer [Lancia](/source/Lancia) has a model called the [Ypsilon](/source/Lancia_Ypsilon).

- In the [International Phonetic Alphabet](/source/International_Phonetic_Alphabet), the symbol ⟨ʋ⟩ is used to represent a [labiodental approximant](/source/Labiodental_approximant).

- In [astrophysics](/source/Astrophysics) and [physical cosmology](/source/Physical_cosmology), ϒ refers to the [mass-to-light ratio](/source/Mass-to-light_ratio).[11]

- In [statistics](/source/Statistics), it is sometimes used instead of v or nu to indicate [degrees of freedom](/source/Degrees_of_freedom_(statistics)).[12]

- In the [Persian](/source/Persian_language) language, “one upsilon” is used to describe a positive amount close to 0 (zero).[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*]

### Similar appearance

- A similar symbol U+2648 ♈ ARIES is used for the [astrological sign](/source/Astrological_sign) of [Aries](/source/Aries_(astrology)).

## Symbolism

[Geoffroy Tory](/source/Geoffroy_Tory) Ypsilon

Upsilon is known as Pythagoras' letter, or the Samian letter, because [Pythagoras](/source/Pythagoras) used it as an emblem of the path of virtue or vice.[13] As the Roman writer [Persius](/source/Persius) wrote in *Satire III*:

and the letter which spreads out into Pythagorean branches has pointed out to you the steep path which rises on the right.[14]

[Lactantius](/source/Lactantius), an early Christian author (c. 240 – c. 320), refers to this:

For they say that the course of human life resembles the letter Y, because every one of men, when he has reached the threshold of early youth, and has arrived at the place "where the way divides itself into two parts," is in doubt, and hesitates, and does not know to which side he should rather turn himself.[15]

## Character encodings

Upsilon and Coptic Ua characters.[16]

- U+01B1 Ʊ LATIN CAPITAL LETTER UPSILON

- U+028A ʊ LATIN SMALL LETTER UPSILON

- U+038E Ύ GREEK CAPITAL LETTER UPSILON WITH TONOS

- U+03A5 Υ GREEK CAPITAL LETTER UPSILON (Υ)

- U+03AB Ϋ GREEK CAPITAL LETTER UPSILON WITH DIALYTIKA

- U+03B0 ΰ GREEK SMALL LETTER UPSILON WITH DIALYTIKA AND TONOS

- U+03C5 υ GREEK SMALL LETTER UPSILON (υ, υ)

- U+03CB ϋ GREEK SMALL LETTER UPSILON WITH DIALYTIKA

- U+03CD ύ GREEK SMALL LETTER UPSILON WITH TONOS

- U+03D2 ϒ GREEK UPSILON WITH HOOK SYMBOL (ϒ, ϒ)

- U+03D3 ϓ GREEK UPSILON WITH ACUTE AND HOOK SYMBOL

- U+03D4 ϔ GREEK UPSILON WITH DIAERESIS AND HOOK SYMBOL

- U+1D7F ᵿ LATIN SMALL LETTER UPSILON WITH STROKE

- U+1DB7 ᶷ MODIFIER LETTER SMALL UPSILON

- U+1F50 ὐ GREEK SMALL LETTER UPSILON WITH PSILI

- U+1F51 ὑ GREEK SMALL LETTER UPSILON WITH DASIA

- U+1F52 ὒ GREEK SMALL LETTER UPSILON WITH PSILI AND VARIA

- U+1F53 ὓ GREEK SMALL LETTER UPSILON WITH DASIA AND VARIA

- U+1F54 ὔ GREEK SMALL LETTER UPSILON WITH PSILI AND OXIA

- U+1F55 ὕ GREEK SMALL LETTER UPSILON WITH DASIA AND OXIA

- U+1F56 ὖ GREEK SMALL LETTER UPSILON WITH PSILI AND PERISPOMENI

- U+1F57 ὗ GREEK SMALL LETTER UPSILON WITH DASIA AND PERISPOMENI

- U+1F59 Ὑ GREEK CAPITAL LETTER UPSILON WITH DASIA

- U+1F5B Ὓ GREEK CAPITAL LETTER UPSILON WITH DASIA AND VARIA

- U+1F5D Ὕ GREEK CAPITAL LETTER UPSILON WITH DASIA AND OXIA

- U+1F5F Ὗ GREEK CAPITAL LETTER UPSILON WITH DASIA AND PERISPOMENI

- U+1F7A ὺ GREEK SMALL LETTER UPSILON WITH VARIA

- U+1F7B ύ GREEK SMALL LETTER UPSILON WITH OXIA

- U+1FE0 ῠ GREEK SMALL LETTER UPSILON WITH VRACHY

- U+1FE1 ῡ GREEK SMALL LETTER UPSILON WITH MACRON

- U+1FE2 ῢ GREEK SMALL LETTER UPSILON WITH DIALYTIKA AND VARIA

- U+1FE3 ΰ GREEK SMALL LETTER UPSILON WITH DIALYTIKA AND OXIA

- U+1FE6 ῦ GREEK SMALL LETTER UPSILON WITH PERISPOMENI

- U+1FE7 ῧ GREEK SMALL LETTER UPSILON WITH DIALYTIKA AND PERISPOMENI

- U+1FE8 Ῠ GREEK CAPITAL LETTER UPSILON WITH VRACHY

- U+1FE9 Ῡ GREEK CAPITAL LETTER UPSILON WITH MACRON

- U+1FEA Ὺ GREEK CAPITAL LETTER UPSILON WITH VARIA

- U+1FEB Ύ GREEK CAPITAL LETTER UPSILON WITH OXIA

- U+2CA8 Ⲩ COPTIC CAPITAL LETTER UA

- U+2CA9 ⲩ COPTIC SMALL LETTER UA

- U+1D6BC 𝚼 MATHEMATICAL BOLD CAPITAL UPSILON

- U+1D6D6 𝛖 MATHEMATICAL BOLD SMALL UPSILON

- U+1D6F6 𝛶 MATHEMATICAL ITALIC CAPITAL UPSILON

- U+1D710 𝜐 MATHEMATICAL ITALIC SMALL UPSILON

- U+1D730 𝜰 MATHEMATICAL BOLD ITALIC CAPITAL UPSILON

- U+1D74A 𝝊 MATHEMATICAL BOLD ITALIC SMALL UPSILON

- U+1D76A 𝝪 MATHEMATICAL SANS-SERIF BOLD CAPITAL UPSILON

- U+1D784 𝞄 MATHEMATICAL SANS-SERIF BOLD SMALL UPSILON

- U+1D7A4 𝞤 MATHEMATICAL SANS-SERIF BOLD ITALIC CAPITAL UPSILON

- U+1D7BE 𝞾 MATHEMATICAL SANS-SERIF BOLD ITALIC SMALL UPSILON

## Notes

1. ^ [***a***](#cite_ref-Chambers_1-0) [***b***](#cite_ref-Chambers_1-1) "upsilon". *[Chambers Dictionary](/source/Chambers_Dictionary)* (9th ed.). [Chambers](/source/Chambers_(publisher)). 2003. [ISBN](/source/ISBN_(identifier)) [0-550-10105-5](https://en.wikipedia.org/wiki/Special:BookSources/0-550-10105-5).

1. **[^](#cite_ref-Collins_2-0)** "upsilon". *[Collins English Dictionary](/source/Collins_English_Dictionary)* (13th ed.). [HarperCollins](/source/HarperCollins). 2018. [ISBN](/source/ISBN_(identifier)) [978-0-008-28437-4](https://en.wikipedia.org/wiki/Special:BookSources/978-0-008-28437-4).

1. **[^](#cite_ref-3)** ["Upsilon"](https://www.merriam-webster.com/dictionary/Upsilon). *[Merriam-Webster.com Dictionary](/source/Merriam-Webster)*. Merriam-Webster. [OCLC](/source/OCLC_(identifier)) [1032680871](https://search.worldcat.org/oclc/1032680871). Retrieved 2016-01-22.

1. **[^](#cite_ref-4)** ["Upsilon"](https://web.archive.org/web/20191221151730/https://www.lexico.com/definition/upsilon). *[Lexico](/source/Lexico) UK English Dictionary*. [Oxford University Press](/source/Oxford_University_Press). Archived from [the original](http://www.lexico.com/definition/Upsilon) on 2019-12-21.

1. **[^](#cite_ref-5)** ["upsilon"](https://www.dictionary.com/browse/upsilon). *[Dictionary.com Unabridged](/source/Dictionary.com)* (Online). n.d. Retrieved 2016-01-22.

1. **[^](#cite_ref-6)** ["upsilon"](https://www.oed.com/search/dictionary/?q=upsilon). *[Oxford English Dictionary](/source/Oxford_English_Dictionary)* (online ed.). Oxford University Press. (Subscription or [participating institution membership](https://www.oed.com/public/login/loggingin#withyourlibrary) required.)

1. **[^](#cite_ref-7)** [W. Sidney Allen](/source/W._Sidney_Allen), *Vox Graeca*, 3rd ed., Cambridge 1987, p. 69.

1. **[^](#cite_ref-8)** Woodard, Roger D. (June 12, 1997). [*Greek Writing from Knossos to Homer: A Linguistic Interpretation of the Origin of the Greek Alphabet and the Continuity of Ancient Greek Literacy*](https://books.google.com/books?id=rXYDQwehOVMC&q=upsilon+%22back+vowel%22). Oxford University Press. [ISBN](/source/ISBN_(identifier)) [9780195355666](https://en.wikipedia.org/wiki/Special:BookSources/9780195355666) – via Google Books.

1. **[^](#cite_ref-9)** Mastronarde, Donald J. (February 21, 2013). [*Introduction to Attic Greek*](https://books.google.com/books?id=qmHsrNYoe4MC&q=upsilon+%22Close+back+rounded+vowel%22+greek&pg=PA12). University of California Press. [ISBN](/source/ISBN_(identifier)) [9780520275713](https://en.wikipedia.org/wiki/Special:BookSources/9780520275713) – via Google Books.

1. **[^](#cite_ref-10)** F. Lauritzen, "Michael the Grammarian's irony about Hypsilon. A step towards reconstructing Byzantine pronunciation", *Byzantinoslavica*, **67** (2009)

1. **[^](#cite_ref-11)** Mihalas and McRae (1968), *Galactic Astronomy* (W. H. Freeman)

1. **[^](#cite_ref-12)** Walpole, Ronald (2017). *Probability and Statistics for Scientists and Engineers* (9th ed.).

1. **[^](#cite_ref-13)** Brewer, Ebenezer Cobham. *The reader's handbook of famous names in fiction, allusions, references, proverbs, plots, stories, and poems*, [Vol. 2, p. 956](https://books.google.com/books?id=n3kjAQAAIAAJ&pg=PA956&q=%22samian%20letter%22). Lippincott, 1899.

1. **[^](#cite_ref-14)** [Persius](/source/Persius) (1920). [*Satires*](https://archive.org/stream/juvenalpersiuswi00juveuoft/juvenalpersiuswi00juveuoft_djvu.txt).

1. **[^](#cite_ref-15)** [Lactatius](/source/Lactantius). [*The Divine Institutes*](https://en.wikisource.org/wiki/Ante-Nicene_Fathers/Volume_VII/Lactantius/The_Divine_Institutes/Book_VI/Chap._III). pp. Book VI Chapter III.

1. **[^](#cite_ref-16)** Unicode Code Charts: [Greek and Coptic (Range: 0370-03FF)](https://www.unicode.org/charts/PDF/U0370.pdf)

## External links

Look up ***[Υ](https://en.wiktionary.org/wiki/%CE%A5)*** or ***[υ](https://en.wiktionary.org/wiki/%CF%85)*** in Wiktionary, the free dictionary.

Wikimedia Commons has media related to [Upsilon (letter)](https://commons.wikimedia.org/wiki/Category:Upsilon_(letter)).

- Merrifield, Michael (2009). ["Υ – Mass to Light Ratio"](http://www.sixtysymbols.com/videos/masstolight.htm). *Sixty Symbols*. [Brady Haran](/source/Brady_Haran) for the [University of Nottingham](/source/University_of_Nottingham).

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Adapted from the Wikipedia article [Upsilon](https://en.wikipedia.org/wiki/Upsilon) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Upsilon?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.