upsilon /ūp-sīˈlon, ŭp-, ūpˈsi- or upˈsi-/ or ypsilon /ip-sīˈlon or ipˈsi-/

1. The twentieth letter of the Greek alphabet (Υ, υ)
2. As a numeral υˈ = 400, ˌυ = 400000
3. A short-lived heavy subatomic particle produced when beryllium nuclei are bombarded with high-energy protons

• energumen
• energumens
• energy
• energy drink
• energy drinks
• energy gap
• energy gaps
• energy level
• energy levels
• energy-mass equation
• enervate
• enervated
• enervates
• enervating
• enervation
• enervations
• enervative
• enerve
• enerved
• enerves
• enerving
• enew
• enewed
• enewing
• enews