Upsilon

This article is about the Greek upsilon. For the Latin upsilon, see ʊ.

"Ypsilon" redirects here. For the bridge in Drammen, Norway, see Ypsilon (bridge). For the car model, see Lancia Ypsilon.

Upsilon (uppercase Υ, lowercase υ; Greek: ύψιλον, ýpsilon, [ˈipsilon]; /ˈʌpsɪlɒn, ˈjuːp-, ˈuːp-, ˈʊp-, -lən/; or UK: /ʌpˈsaɪlən, juːp-/) is the 20th letter of the Greek alphabet. In the system of Greek numerals, Υʹ has a value of 400. It is derived from the Phoenician waw .

The Greek alphabet on a black figure vessel, with a V-shaped upsilon

Etymology

The name of the letter was originally just “υ” (y; also called hy, hence "hyoid", meaning "shaped like the letter υ"), but the name changed to “υ ψιλόν”, (u psilon, meaning 'simple u') to distinguish it from οι, which had come to have the same [y] pronunciation.

Pronunciation

In early Greek it was pronounced like English oo [u]. In Classical Greek, it was pronounced like French u or German ü, i.e., [y] (a sound that is not found in most dialects of English). This was the case at least until the year 1030AD. In Modern Greek it is pronounced like continental i or English ee, [i], and in diphthongs, [f] or [v]. In ancient Greek, it occurred in both long and short versions, but this distinction has been lost in Modern Greek.

As an initial letter in Classical Greek it always carried the rough breathing (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 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, which have subsequently developed in various ways: For instance, after alpha or epsilon it is pronounced [f] or [v] in Modern Greek.

Correspondence with Latin Y

Cyrillic У, Latin Y and Greek Υ and ϒ in FreeSerif – one of the few typefaces that distinguishes between the Latin and the Greek form

The usage of 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 Claudius proposed introducing a new letter into the 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 arose from it: V and Y and, much later, U and W. In the Cyrillic script, the letters U (У, у) and izhitsa (Ѵ, ѵ) arose from it.

In some languages (most notably German), the name upsilon (Ypsilon in German, ípsilon in Portuguese) is used to refer to the Latin letter Y as well as the Greek letter.

Usage

• In particle physics the capital Greek letter Υ denotes an Upsilon particle. Note that the symbol should always look like $\,\Upsilon$ in order to avoid confusion with a Latin Y denoting the hypercharge.
• Automobile manufacturer Lancia has a model called the Ypsilon. See Lancia Ypsilon.
• In linguistics, the symbol is used to represent a labiodental approximant.
• In astrophysics and physical cosmology, $\Upsilon$ refers to the mass-to-light ratio.

Symbolism

Geoffroy Tory Ypsilon

Upsilon is known as Pythagoras' letter, or the Samian letter, because Pythagoras used it as an emblem of the path of virtue or vice. As the Roman writer 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.

Lactantius, an early Christian author (ca. 240 – ca. 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.

Character encodings

• Greek Upsilon

Character information

Preview	Υ		υ		ϒ
Unicode name	GREEK CAPITAL LETTER UPSILON		GREEK SMALL LETTER UPSILON		GREEK UPSILON WITH HOOK SYMBOL
Encodings	decimal	hex	dec	hex	dec	hex
Unicode	933	U+03A5	965	U+03C5	978	U+03D2
UTF-8	206 165	CE A5	207 133	CF 85	207 146	CF 92
Numeric character reference	Υ	Υ	υ	υ	ϒ	ϒ
Named character reference	Υ		υ, υ		ϒ, ϒ
DOS Greek	148	94	172	AC
DOS Greek-2	209	D1	239	EF
Windows 1253	213	D5	245	F5
TeX	\Upsilon		\upsilon

• Coptic Ua

Character information

Preview	Ⲩ		ⲩ
Unicode name	COPTIC CAPITAL LETTER UA		COPTIC SMALL LETTER UA
Encodings	decimal	hex	dec	hex
Unicode	11432	U+2CA8	11433	U+2CA9
UTF-8	226 178 168	E2 B2 A8	226 178 169	E2 B2 A9
Numeric character reference	Ⲩ	Ⲩ	ⲩ	ⲩ

• Latin Upsilon

Character information

Preview	Ʊ		ʊ		ᶷ		ᵿ
Unicode name	LATIN CAPITAL LETTER UPSILON		LATIN SMALL LETTER UPSILON		MODIFIER LETTER SMALL UPSILON		LATIN SMALL LETTER UPSILON WITH STROKE
Encodings	decimal	hex	dec	hex	dec	hex	dec	hex
Unicode	433	U+01B1	650	U+028A	7607	U+1DB7	7551	U+1D7F
UTF-8	198 177	C6 B1	202 138	CA 8A	225 182 183	E1 B6 B7	225 181 191	E1 B5 BF
Numeric character reference	Ʊ	Ʊ	ʊ	ʊ	ᶷ	ᶷ	ᵿ	ᵿ

• Mathematical Upsilon

Character information

Preview	𝚼		𝛖		𝛶		𝜐		𝜰		𝝊
Unicode name	MATHEMATICAL BOLD CAPITAL UPSILON		MATHEMATICAL BOLD SMALL UPSILON		MATHEMATICAL ITALIC CAPITAL UPSILON		MATHEMATICAL ITALIC SMALL UPSILON		MATHEMATICAL BOLD ITALIC CAPITAL UPSILON		MATHEMATICAL BOLD ITALIC SMALL UPSILON
Encodings	decimal	hex	dec	hex	dec	hex	dec	hex	dec	hex	dec	hex
Unicode	120508	U+1D6BC	120534	U+1D6D6	120566	U+1D6F6	120592	U+1D710	120624	U+1D730	120650	U+1D74A
UTF-8	240 157 154 188	F0 9D 9A BC	240 157 155 150	F0 9D 9B 96	240 157 155 182	F0 9D 9B B6	240 157 156 144	F0 9D 9C 90	240 157 156 176	F0 9D 9C B0	240 157 157 138	F0 9D 9D 8A
UTF-16	55349 57020	D835 DEBC	55349 57046	D835 DED6	55349 57078	D835 DEF6	55349 57104	D835 DF10	55349 57136	D835 DF30	55349 57162	D835 DF4A
Numeric character reference	𝚼	𝚼	𝛖	𝛖	𝛶	𝛶	𝜐	𝜐	𝜰	𝜰	𝝊	𝝊

Character information

Preview	𝝪		𝞄		𝞤		𝞾
Unicode name	MATHEMATICAL SANS-SERIF BOLD CAPITAL UPSILON		MATHEMATICAL SANS-SERIF BOLD SMALL UPSILON		MATHEMATICAL SANS-SERIF BOLD ITALIC CAPITAL UPSILON		MATHEMATICAL SANS-SERIF BOLD ITALIC SMALL UPSILON
Encodings	decimal	hex	dec	hex	dec	hex	dec	hex
Unicode	120682	U+1D76A	120708	U+1D784	120740	U+1D7A4	120766	U+1D7BE
UTF-8	240 157 157 170	F0 9D 9D AA	240 157 158 132	F0 9D 9E 84	240 157 158 164	F0 9D 9E A4	240 157 158 190	F0 9D 9E BE
UTF-16	55349 57194	D835 DF6A	55349 57220	D835 DF84	55349 57252	D835 DFA4	55349 57278	D835 DFBE
Numeric character reference	𝝪	𝝪	𝞄	𝞄	𝞤	𝞤	𝞾	𝞾

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

• Merrifield, Michael (2009). "γ – Mass to Light Ratio". Sixty Symbols. Brady Haran for the University of Nottingham.