Upsilon

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  ·  ·  ·  ·  ·
Ligatures (ϛ, ȣ, ϗ) · Diacritics
Numerals: (6) · (90) · (900)
In other languages
Bactrian  · Coptic  · Albanian
Scientific symbols
Book  · Category · Commons

Upsilon (uppercase Υ, lowercase υ; Greek: Ύψιλον, Úpsilon) is the 20th letter of the Greek alphabet.  In the system of Greek numerals it has a value of 400. It is derived from the Phoenician waw. The name of the letter is pronounced [ˈipsilon] in Modern Greek, and in English /ˈʌpsɨlɒn/, UK: /juːpˈsaɪlən/ yewp-sy-lən, or US: /ˈjuːpsɨlɒn/ yewp-sə-lon. It is occasionally called "ypsilon" (/ˈɪpsɨlɒn/) in English after its rendering in Latin, where the Greek upsilon corresponded with the letter Y.

Contents 1 Pronunciation 2 Correspondence with Latin Y 3 Usage 4 Symbolism 5 Notes

Pronunciation

In early Greek and modern physics it is pronounced  oo [u] . In Classical Greek, it was pronounced like French u or German ü, [y]—a sound that is not found in most dialects of English. This was the case at least until the year 1030AD.^[1] 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 which 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].

Correspondence with Latin Y

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 by most people except the educated ones. 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 was sometimes used for Greek upsilon instead.

The name of the letter was originally just υ (y; also called hy, hence "hyoid", meaning "y-shaped"). It changed to υ ψιλόν, (u psilon, meaning 'simple u') to distinguish it from οι, which had come to have the same [y] pronunciation.^[2]  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, (üppsilon) 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 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.

Symbolism

Upsilon is known as Pythagoras' letter, or the Samian letter, because Pythagoras used it as an emblem of the path of virtue or vice.^[3] 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."^[4]

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."^[5]

Notes