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Upsilon (Υ, υ) Definition

Upsilon (Υ, υ) or ypsilon 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 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 simple u to distinguish it from οι, which had come to have the same [y] pronunciation.

Pronunciation

In early Greek, it was pronounced [u]. In Classical Greek, it was pronounced [y], at least until 1030. In Modern Greek, it is pronounced [i]; in the digraphs αυ and ευ, as [f] or [v]. In ancient Greek, it occurred in both 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 (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.

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 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 Mathematics & Science

The uppercase (Υ) & lowercase (υ) Upsilon are used for:

  • In particle physics the capital Greek letter Υ denotes an Upsilon particle. Note that the symbol should always look like Υ 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 ʋ is used to represent a labiodental approximant.

  • In astrophysics and physical cosmology, Υ refers to the mass-to-light ratio.

  • A similar symbol is used for the astrological sign of Aries.

Greek Alphabet

The letters of the Ancient Greek Alphabet, which are frequently utilized in math and science:

Greek Alphabet

Symbol

Letter

Symbol

Letter

Uppercase

Lowercase

Uppercase

Lowercase

Α

α

Alpha

Ν

ν

Nu

Β

β

Beta

Ξ

ξ

Xi

Γ

γ

Gamma

Ο

ο

Omicron

Δ

δ

Delta

Π

π

Pi

Ε

ε

Epsilon

Ρ

ρ

Rho

Ζ

ζ

Zeta

Σ

σ

Sigma

Η

η

Eta

Τ

τ

Tau

Θ

θ

Theta

Υ

υ

Upsilon

Ι

ι

Iota

Φ

φ

Phi

Κ

κ

Kappa

Χ

χ

Chi

Λ

λ

Lambda

Ψ

ψ

Psi

Μ

μ

Mu

Ω

ω

Omega

Related Definitions

Sources

“Upsilon.” Wikipedia, Wikimedia Foundation, 6 Apr. 2020, en.wikipedia.org/wiki/Upsilon.

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