upsilon
/juːpˈsaɪlən/noun
1- the twentieth letter of the Greek alphabet (Υ, υ), transliterated as 'u' or (chiefly in English words derived through Latin) as 'y'希腊字母表中第二十个字母(Υ, υ)（译写为u或y, 后者多见于源自拉丁语的英语单词中）。
1.1
Upsilon
followed by Latin genitive Astronomy the twentieth star in a constellation【天文】υ星（星座中第二十颗星）：Upsilon Scorpii.
天蝎座υ星。
1.2
- （亦作upsilon particle）Physics a meson thought to contain a b quark bound to its antiparticle, produced in particle accelerators【物】υ粒子。
词源
Greek, literally 'slender U', from psilos 'slender', referring to the need to distinguish upsilon from the diphthong oi： in late Greek the two had the same pronunciation.