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

• acidly
• acidness
• acidnesses
• acidophil
• acidophilic
• acidophils
• acidophilus
• acidophiluses
• acidoses
• acidosis
• acid rain
• acid reflux
• acid rock
• acid rocks
• acids
• acid salt
• acid salts
• acid soil complex
• acid test
• acid tests
• acidulate
• acidulated
• acidulates
• acidulating
• acidulent