Upsilon (uppercase Υ, lowercase υ; _el. Ύψιλον) is the 20th letter of the
Greek alphabet. In the system of Greek numeralsit has a value of 400. It is derived from the Phoenician waw.
In early Greek it was pronounced like English "oo," IPA2|u . In
Classical Greek, it was pronounced like French "u" or German "ü", IPA2|y — a sound that is not found in most dialects of English. In Modern Greekit is pronounced like continental "i" or English "ee", IPA2|i, and in diphthongs, IPA| [f] or IPA| [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] .
Roman Emperor Claudiusproposed introducing a new letter into the Latin alphabetto approximate the sound of upsilon, but in due course the letter Y was adopted 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 IPA| [y] pronunciation. [See W. Sidney Allen, "Vox Graeca", 3rd ed., Cambridge 1987, p. 69.] The name of the letter in modern Greek is pronounced IPA|/iː'psɪlɒn/ (in contrast to the letter Ε, which is pronounced IPA|/ɛ'psɪlɒn/). It is also rarely called "ypsilon" (IPA|/ɪ'psɪlɒn/) in English because of its resemblance to the Roman letter Y.
Four letters of the
Latin alphabetarose from it: Vand Yand, much later, Uand W. In the Cyrillic alphabet, the letters U (у) and Izhitsa(ѵ) arose from it.
particle physicsthe 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.
Lanciahas a model called the Ypsilon. See Lancia Ypsilon.
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