- the twentieth letter of the Greek alphabet (?, ?)
- ⌂ any of a group of short-lived elementary particles having a mass about ten times greater than that of a proton
Origin of upsilonLate Greek y psilon, literally , simple u (to distinguish from oi, of the same sound in LGr)
The 20th letter of the Greek alphabet. See Table at alphabet.
Origin of upsilonLate Greek &umacron; ps&imacron;lon, simple u (from the fact that oi was given the same pronunciation in Late Greek as u) : &umacron;, h&umacron;, the letter U + ps&imacron;lon, neuter of ps&imacron;los, simple (written with one letter as opposed to two).
(plural upsilons or upsila)