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Definition of upsilon

upsilon

/ˈuːpsɪlɒn/
up · si · lon
Plural:upsilons
•
Adjective:upsilonic
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upsilon Lexical Profile

upsilon Game Scores & Validity

• noun

1

The twentieth letter of the Greek alphabet (Υ, υ), transliterated in the Roman alphabet as 'u' or 'y'.

Example

"In the International Phonetic Alphabet, a symbol resembling a lowercase upsilon represents a near-close near-back rounded vowel."

2

In particle physics, a flavourless meson composed of a bottom quark and its antiquark, denoted by the uppercase Greek symbol Υ.

Example

"The discovery of the upsilon meson at Fermilab in 1977 provided the first experimental evidence for the existence of the bottom quark."

• Nearby Words

upside
upside down catfish
upsies
upsilon
upsize
upskill
upskirt

Word Origin & Etymology

Borrowed from Medieval Greek 'u psilon' (literally 'bare u' or 'simple u'), a name coined by Byzantine grammarians to distinguish the single letter Υ from the identically pronounced digraph οι.

Cite this Entry

Wordmom. (2026). Definition of Upsilon. In Wordmom Dictionary. Retrieved Nov 5, 2026, from https://wordmom.com/dictionary/upsilon
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