The name of the letter was originally justυ (y, also calledὑhy, hencehyoid, meaning 'shaped like the letterυ'), but the name changed toυ ψιλόν (=υpsilon, 'u-plain' or 'u-simple') to distinguish it fromοι, which had come to have the same[y] pronunciation.[7]
As an initial letter in Classical Greek, it always carried therough breathing (equivalent toh) as reflected in the manyGreek-derived English words, such as those that begin withhyper- andhypo-. This rough breathing was derived from an older pronunciation that used asibilant instead; this sibilant was not lost in Latin, giving rise to such cognates assuper- (forhyper-) andsub- (forhypo-).
Upsilon participated as the second element infalling diphthongs, which have subsequently developed in various ways.
CyrillicУ,LatinY and GreekΥ (upsilon) andϒ (hooked upsilon) inFreeSerif – one of the few typefaces that distinguish between the Latin and the Greek form.
The usage ofY 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. TheRoman EmperorClaudius proposed introducing anew letter into theLatin alphabet to transcribe the so-calledsonus medius (a short vowel before labial consonants), but in inscriptions, the new letter was sometimes used for Greek upsilon instead.
In some languages, includingGerman andPortuguese, the nameupsilon (Ypsilon in German,ípsilon in Portuguese) is used to refer to the Latin letterY as well as the Greek letter. In some other languages, the (Latin) Y is referred to as a "Greek I" (i griega inSpanish,i grec inFrench), also noting its Greek origin.
Inparticle physics the capital Greek letter ϒ denotes anUpsilon particle. Note that the symbol should always look like in order to avoid confusion with a Latin Y denoting thehypercharge. This may be done either with a font such as FreeSerif or with the dedicated Unicode character U+03D2 ϒ.
Automobile manufacturerLancia has a model called theYpsilon.
Upsilon is known as Pythagoras' letter, or the Samian letter, becausePythagoras used it as an emblem of the path of virtue or vice.[13] As the Roman writerPersius wrote inSatire III:
and the letter which spreads out into Pythagorean branches has pointed out to you the steep path which rises on the right.[14]
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.[15]
^F. Lauritzen, "Michael the Grammarian's irony about Hypsilon. A step towards reconstructing Byzantine pronunciation",Byzantinoslavica,67 (2009)
^Mihalas and McRae (1968),Galactic Astronomy (W. H. Freeman)
^Walpole, Ronald (2017).Probability and Statistics for Scientists and Engineers (9th ed.).
^Brewer, Ebenezer Cobham.The reader's handbook of famous names in fiction, allusions, references, proverbs, plots, stories, and poems,Vol. 2, p. 956. Lippincott, 1899.
