upsilon

play
noun up·si·lon \ ˈüp-sə-ˌlän , ˈyüp- , ˈəp- , -lən , British usually yüp-ˈsī-lən \

Definition of upsilon

1 :the 20th letter of the Greek alphabet — see Alphabet Table
2 :any of a group of unstable electrically neutral elementary particles of the meson family that have a mass about 10 times that of a proton

Origin and Etymology of upsilon

Middle Greek y psilon, literally, simple y; from the desire to distinguish it from oi, which was pronounced the same in later Greek


Learn More about upsilon


Seen and Heard

What made you want to look up upsilon? Please tell us where you read or heard it (including the quote, if possible).

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

WORD OF THE DAY

to curse or denounce

Get Word of the Day daily email!

Test Your Vocabulary

Merriam-Webster's New Words Quiz—Fall 2017 Edition!

  • young-plant-shoots
  • Which of the following is a new sense of the word bunny?
Spell It

Can you spell these 10 commonly misspelled words?

TAKE THE QUIZ
Citation

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!