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• epsilon
  epsilon

  noun

  the fifth letter of the Greek alphabet (E, ε).
• Epsilon
  Epsilon

  noun

  (foll by the genitive case of a specified constellation) the fifth brightest star in a constellation

epsilon

American  

[ep-suh-lon, -luhn, ep-sahy-luhn] / ˈɛp səˌlɒn, -lən, ɛpˈsaɪ lən /

noun

1. the fifth letter of the Greek alphabet (E, ε).

2. the consonant sound represented by this letter.

3. Mathematics. an arbitrarily small quantity, used to indicate that a given quantity is small, or close to zero.

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Epsilon ¹ British  

/ ˈɛpsɪˌlɒn, ɛpˈsaɪlən /

noun

1. (foll by the genitive case of a specified constellation) the fifth brightest star in a constellation

   Epsilon Aurigae

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epsilon ² British  

/ ˈɛpsɪˌlɒn, ɛpˈsaɪlən /

noun

1. the fifth letter of the Greek alphabet (Ε, ε), a short vowel, transliterated as e

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Etymology

Origin of epsilon

First recorded in 1400–50; from Greek e psīlón “bare, simple e ” (as opposed to diphthongal spellings which in later Greek represented the same sound)

Example Sentences

See Examples For:

epsilon Epsilon

For the three stars with detected astrospheres, named 70 Ophiuchi, epsilon Eridani, and 61 Cygni, the researchers estimated their mass loss rates to be 66.5±11.1, 15.6±4.4, and 9.6±4.1 times the solar mass loss rate, respectively.

From Science Daily ● Apr. 12, 2024

A few others made the rogue’s gallery of variants: gamma, beta, epsilon.

From Washington Post ● Aug. 8, 2021

Another delta mutation — also found in kappa and epsilon — is called L452R.

From Salon ● Jul. 29, 2021

You could replace an image of the novel coronavirus with an image from 2006 of an epsilon 15 bacteriophage, a virus that infects salmonella, and few of us would raise an eyebrow.

From Slate ● Mar. 24, 2020

There were five city quarters, designated by the Greek letters alpha through epsilon.

From "Circumference" by Nicholas Nicastro

Epsilon Indi Ab orbits about four times farther from its star than Jupiter does from the Sun.

From Science Daily ● Apr. 22, 2026

Their next-door neighbors are three Delta Kappa Epsilon fraternity brothers developing AI that helps insurance companies sell more policies.

From The Wall Street Journal ● Apr. 4, 2026

Named Epsilon Indi, the star is the smallest and coolest dwarf star yet observed with solar-like oscillations -- "starquakes" like those shown by the Sun.

From Science Daily ● Mar. 26, 2024

The Sigma Alpha Epsilon Fraternity Service Center, in a statement to WBRC, said the national organization is investigating what happened at the Alabama chapter and is cooperating with the university and law enforcement investigation.

From Seattle Times ● Sep. 24, 2023

Could the individual Epsilon embryo be made a revert, by a suitable technique, to the normality of dogs and cows?

From "Brave New World" by Aldous Huxley