Upsilon (; or ; uppercase Υ, lowercase υ; el, ''ýpsilon'' ) or ypsilon is the 20th letter of the
Greek alphabet The Greek alphabet has been used to write the Greek language since the late ninth or early eighth century BC. It is derived from the earlier Phoenician alphabet, and was the first alphabetic script in history to have distinct letters for vowels ...

Greek alphabet
. In the system of
Greek numerals Greek numerals, also known as Ionic, Ionian, Milesian, or Alexandrian numerals, are a numeral system, system of writing numbers using the letters of the Greek alphabet. In modern Greece, they are still used for ordinal number (linguistics), ordi ...
, grc, Υʹ, label=none has a value of 400. It is derived from the
Phoenician Phoenician may refer to: * Phoenicia, an ancient civilization * Phoenician alphabet * Phoenician language * List of Phoenician cities * Phoenix, Arizona See also

* Phoenix (mythology) * Phoenicia (disambiguation) {{disambiguation Language an ...

waw .


The name of the letter was originally just "υ" (''y;'' also called ''hy'', hence "
hyoid The hyoid bone (lingual bone or tongue-bone) () is a horseshoe , and are nailed to the underside of the hoof A horseshoe is a fabricated product, normally made of metal, although sometimes made partially or wholly of modern synthetic materials, ...
", meaning "shaped like the letter υ"), but the name changed to "υ ψιλόν" ''u psilon'' 'simple u' to distinguish it from οι, which had come to have the same pronunciation.


In early
Attic Greek Attic Greek is the dialect of the of , including the ' of . Often called classical Greek, it was the dialect of the for centuries and remains the standard form of the language that is taught to students of . As the basis of the Hellenistic , ...
(6th century BCE), it was pronounced (a
close back rounded vowel The close back rounded vowel, or high back rounded vowel, is a type of vowel A vowel is a syllabicSyllabic may refer to: *Syllable, a unit of speech sound, considered the building block of words **Syllabic consonant, a consonant that forms th ...
like the English "long o͞o"). In
Classical Greek Ancient Greek includes the forms of the Greek language Greek (modern , romanized: ''Elliniká'', Ancient Greek, ancient , ''Hellēnikḗ'') is an independent branch of the Indo-European languages, Indo-European family of languages, nati ...
, it was pronounced (a
close front rounded vowel The close front rounded vowel, or high front rounded vowel, is a type of vowel sound, used in some spoken languages. The symbol in the International Phonetic Alphabet that represents this sound is /y/, and the equivalent X-SAMPA symbol is y. Acro ...
), at least until 1030. In
Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply as Greek (, ), refers collectively to the dialects of the Greek language spoken in the modern era, including the official standardized form of the l ...
, it is pronounced ; in the
digraph Digraph may refer to: * Digraph (orthography), a pair of characters used together to represent a single sound, such as "sh" in English * Orthographic ligature, the joining of two letters as a single glyph, such as "æ" * Digraph (computing), a grou ...
s and , as or . In ancient Greek, it occurred in both
long and short
long and short
versions, but Modern Greek does not have a length distinction. As an initial letter in Classical Greek, it always carried the
rough breathing In the polytonic orthography Greek orthographyThe orthography of the Greek language ultimately has its roots in the adoption of the Greek alphabet in the 9th century BC. Some time prior to that, one early form of Greek, Mycenaean language, My ...
(equivalent to ''h'') as reflected in the many Greek-derived English words, such as those that begin with ''hyper-'' and ''hypo-''. This rough breathing was derived from an older pronunciation that used a
sibilant In phonetics Phonetics is a branch of linguistics that studies how humans produce and perceive sounds, or in the case of sign languages, the equivalent aspects of sign. Phoneticians—linguists who specialize in phonetics—study the physical pr ...
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 diphthong A diphthong ( ; , ), also known as a gliding vowel, is a combination of two adjacent vowel sounds within the same syllable. Technically, a diphthong is a vowel with two different targets: that is, the tongue (and/or other parts of the speech or ...
s, which have subsequently developed in various ways.

Correspondence with Latin Y

The usage of
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 or . The latter pronunciation was the most common in the Classical period and was used mostly by uneducated people. The
Roman Emperor The Roman emperor was the ruler of the Roman Empire during the History of the Roman Empire, imperial period (starting in 27 BC). The emperors used a variety of different titles throughout history. Often when a given Roman is described as becom ...
Claudius Claudius ( ; Tiberius Claudius Caesar Augustus Germanicus; 1 August 10 BC – 13 October AD 54) was the fourth Roman emperor The Roman emperor was the ruler of the Roman Empire during the History of the Roman Empire, imperial p ...

proposed introducing a
new letter
new letter
into the
Latin alphabet The Latin alphabet or Roman alphabet is the collection of letters originally used by the ancient Romans In historiography Historiography is the study of the methods of historian ( 484– 425 BC) was a Greek historian who lived ...

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 The Latin alphabet or Roman alphabet is the collection of letters originally used by the ancient Romans In historiography Historiography is the study of the methods of historian ( 484– 425 BC) was a Greek historian who lived ...

Latin alphabet
arose from it:
and, much later,
. In the
Cyrillic script The Cyrillic script ( ) is a writing system used for various languages across Eurasia and is used as the national script in various Slavic languages, Slavic, Turkic languages, Turkic, Mongolic languages, Mongolic, Uralic languages, Uralic, Caucas ...
, the letters U (У, у) and
izhitsa Izhitsa (Ѵ, ѵ; italics: ''Ѵ ѵ''; OCS: Ѷжица, russian: И́жица) is a letter of the early Cyrillic alphabet The Early Cyrillic alphabet, also called classical Cyrillic or paleo-Cyrillic, is a writing system A writing sys ...

(Ѵ, ѵ) arose from it. In some languages, including
German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of Germany, see also German nationality law * German language The German la ...

Portuguese Portuguese may refer to: * anything of, from, or related to the country and nation of Portugal ** Portuguese cuisine, traditional foods ** Portuguese language, a Romance language *** Portuguese dialects, variants of the Portuguese language ** Portug ...

, 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 Spanish may refer to: * Items from or related to Spain: **Spaniards, a nation and ethnic group indigenous to Spain **Spanish language **Spanish cuisine Other places * Spanish, Ontario, Canada * Spanish River (disambiguation), the name of several ...

, ''i grec'' in
), also noting its Greek origin.


* In
particle physics Particle physics (also known as high energy physics) is a branch of physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which rel ...
the capital Greek letter ϒ denotes an
Upsilon particle The Upsilon meson () is a quarkonium state (i.e. flavourless meson In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (e ...
. Note that the symbol should always look like \,\Upsilon in order to avoid confusion with a Latin Y denoting the
hypercharge In particle physics, the hypercharge (a portmanteau of hyperon, hyperonic and charge (physics), charge) ''Y'' of a subatomic particle, particle is a quantum number conserved under the strong interaction. The concept of hypercharge provides a singl ...
. This may be done either with a font such as FreeSerif or with the dedicated Unicode character U+03D2 ϒ. * Automobile manufacturer
Lancia Lancia () is an Italian car manufacturer This is a list of notable automobile manufacturers with articles on Wikipedia by country. It includes companies that are in business as well as defunct manufacturers. Only companies that have articles ...

has a model called the Ypsilon. See
Lancia Ypsilon The Lancia Ypsilon is a supermini manufactured and marketed by Lancia, now in its third generation, solely in the domestic Italian market and — as of 2014 — the marque's only model. The Ypsilon was released in 1995, as a larger and m ...

Lancia Ypsilon
. * In the
International Phonetic Alphabet The International Phonetic Alphabet (IPA) is an alphabetic system of phonetic transcription, phonetic notation based primarily on the Latin script. It was devised by the International Phonetic Association in the late 19th century as a standa ...
, the symbol is used to represent a
labiodental approximant The voiced labiodental approximant is a type of consonant In articulatory phonetics, a consonant is a speech sound that is articulated with complete or partial closure of the vocal tract. Examples are , pronounced with the lips; , pronounced with ...

labiodental approximant
. * In
astrophysics Astrophysics is a science that employs the methods and principles of physics in the study of astronomical objects and phenomena. Among the subjects studied are the Sun, other stars, galaxy, galaxies, extrasolar planets, the interstellar medium and ...
physical cosmology Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of fun ...
, ϒ refers to the
mass-to-light ratioIn astrophysics Astrophysics is a science that employs the methods and principles of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural ...
. * In
statistics Statistics is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data Data (; ) are individual facts, statistics, or items of information, often numeric. In a more technical sens ...

, it is sometimes used instead of v or nu to indicate
degrees of freedom Degrees of Freedom (often abbreviated df or DOF) refers to the number of independent variables or parameters of a system. In various scientific fields, the word "freedom" is used to describe the limits to which physical movement or other physical ...

Similar appearance

* A similar symbol (Unicode ♈ U+2648) is used for the
astrological sign In Western astrology, astrological signs are the twelve 30° sectors of the ecliptic, starting at the March equinox, vernal equinox (one of the intersections of the ecliptic with the celestial equator), also known as the First Point of Aries. T ...
Aries Aries may refer to: *Aries (astrology) *Aries (constellation) Vehicles *Dodge Aries, an automobile *Ariès, a French automobile *Aries Motorsport, a British kit car manufacturer *EP-3E Aries, an reconnaissance aircraft Other uses *Aries (rocket) * ...


Upsilon is known as Pythagoras' letter, or the Samian letter, because
Pythagoras Pythagoras of Samos, or simply ; in Ionian Greek () was an ancient Ionians, Ionian Ancient Greek philosophy, Greek philosopher and the eponymous founder of Pythagoreanism. His political and religious teachings were well known in Magna Graec ...

used it as an emblem of the path of virtue or vice. As the Roman writer
Persius Aulus Persius Flaccus (; 4 December 3424 November 62 AD) was a Ancient Rome, Roman poet and satirist of Etruscan civilization, Etruscan origin. In his works, poems and satires, he shows a Stoicism, Stoic wisdom and a strong criticism for what he c ...

wrote in ''Satire III'':
Lactantius Lucius Caecilius Firmianus Lactantius (c. 250 – c. 325) was an early Christian The history of Christianity concerns the Christian religion Christianity is an Abrahamic The Abrahamic religions, also referred to collectively as the ...

, an early Christian author (ca. 240 – ca. 320), refers to this:

Character encodings

* Greek Upsilon Unicode Code Charts
Greek and Coptic (Range: 0370-03FF)
/ref> * Coptic Ua * Latin Upsilon * Mathematical Upsilon These 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.


External links

* {{cite web, last=Merrifield, first=Michael, title=Υ – Mass to Light Ratio, url=http://www.sixtysymbols.com/videos/masstolight.htm, work=Sixty Symbols, publisher=
Brady Haran Brady John Haran (born 18 June 1976) is an Australian-British independent film An independent film, independent movie, indie film, or indie movie is a feature film A feature film, or feature-length film, is a narrative film (motion pictu ...
for the
University of Nottingham , mottoeng = A city is built on wisdom , established = 1798 – teacher training college1881 – University College Nottingham1948 – university status , type = Public In public relations Public relations (PR) ...
, year=2009 Greek letters Vowel letters