| 释义 |
up·si·lon
I. \ˈyüpsəˌlän, ˈəp-, -_lən, Brit yüpˈsīlən\ noun
(-s)
Etymology: Middle Greek y psilon, ypsilon, literally, simple upsilon, from Greek y upsilon + psilon, neuter of psilos simple, mere, bare; from the desire to distinguish between graphic y and graphic oi, pronounced the same in later Greek — more at psil-
: the 20th letter of the Greek alphabet — symbol Υ or υ; see alphabet table
II. noun
: any of a group of unstable electrically neutral subatomic particles of the meson family that have a mass about 10 times that of a proton and are held to consist of a bottom quark-antiquark pair |