[yoop-suh-lon, -luh
n, uhp-; especially Brit. yoop-sahy-luhn] 
| 1. | the 20th letter of the Greek alphabet (Υ, υ). |
| 2. | the vowel sound represented by this letter. |
| 3. | Also called upsilon particle. Physics. any of a family of heavy, short-lived, neutral mesons that are composed of a bottom quark and its antiquark. Symbol: Υ, υ |
| up·si·lon (ŭp'sə-lŏn', yōōp'-) n. The 20th letter of the Greek alphabet. See Table at alphabet. [Late Greek ū psīlon, simple u (from the fact that oi was given the same pronunciation in Late Greek as u) : ū, hū, the letter U + psīlon, neuter of psīlos, simple (written with one letter as opposed to two).] |
upsilon up·si·lon or yp·si·lon (ŭp'sə-lŏn', y&oomacr;p'-)
n.
Symbol υ The 20th letter of the Greek alphabet.