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

• attenuated
• attenuated vaccine
• attenuated vaccines
• attenuates
• attenuating
• attenuation
• attenuations
• attenuator
• attenuators
• attercop
• attercops
• attest
• attestable
• attestation
• attestations
• attestative
• attested
• attester
• attesters
• attesting
• attestor
• attestors
• attests
• Att.-Gen.
• at that