# upsilon

> English word · Noun · IPA /ˈ(j)uːpsɪˌlɒn/ · frequency rank #90,030

## Definitions
1. The twentieth letter of Classical and Modern Greek; the twenty-second letter of Old and Ancient Greek.
2. An upsilon meson, or bottomonium.

## Etymology
From Ancient Greek ὖ ψιλόν (û psilón, “simple Υ”).

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/upsilon