Epsilon

This article is about Greek epsilon. For Latin epsilon, see ɛ.

Look up Ε, ε in Wiktionary, the free dictionary.

Greek alphabet

Αα Alpha	Νν Nu
Ββ Beta	Ξξ Xi
Γγ Gamma	Οο Omicron
Δδ Delta	Ππ Pi
Εε Epsilon	Ρρ Rho
Ζζ Zeta	Σσς Sigma
Ηη Eta	Ττ Tau
Θθ Theta	Υυ Upsilon
Ιι Iota	Φφ Phi
Κκ Kappa	Χχ Chi
Λλ Lambda	Ψψ Psi
Μμ Mu	Ωω Omega
Obsolete letters
Digamma	Qoppa
San	Sampi

Greek diacritics

Epsilon (uppercase Ε, lowercase ε; Greek: Έψιλον) is the fifth letter of the Greek alphabet, corresponding phonetically to a close-mid front unrounded vowel /e/. In the system of Greek numerals it has a value of 5. It was derived from the Phoenician letter He . Letters that arose from Epsilon include the Roman E and Cyrillic Ye.

"Epsilon" (ἒ ψιλόν, "simple e") was coined in the Middle Ages to distinguish the letter from the diphthong αι, which started being pronounced the same way during the period of New Testament Greek.

The standard symbol for lowercase epsilon is the lunate epsilon ϵ (\epsilon, $\epsilon\,$ , in LaTeX), which has its origins in Medieval Greek.

In mathematical notation, the minuscule open e symbol ɛ (\varepsilon, $\varepsilon$ , in LaTeX) from the extended Latin alphabet is often used interchangeably with the lunate epsilon.

The lunate epsilon ϵ is not to be confused with the set symbol $\in$ or falsely recognized as the lunate version Σ (Sigma).

Upper case: character code 0395 Lower case: character code 03B5

[edit] Symbol

The upper-case Epsilon is not a commonly-used symbol outside of the Greek language because of its similarity to the Roman letter E.

The lower-case epsilon, ε/ϵ, or open e, ɛ, (see above) is used as the symbol for:

In mathematics (particularly calculus), an arbitrarily (or nearly so) small positive quantity is commonly denoted ε; see limit.
- By analogy with this, the late mathematician Paul Erdős also used the term "epsilons" to refer to children (Hoffman 1998, p. 4).
In mathematics, the Levi-Civita symbol.
In mathematics, to represent the dual numbers: a + bε, with ε²=0 and ε≠0.
In mathematics, sometimes used to denote the Heaviside step function
In set theory, the limit ordinal of the sequence $\omega,\omega^{\omega},\omega^{\omega^{\omega}},\dots$ .
In computing, the precision of a numeric data type and floating-point machine epsilon.
In computer science, the empty string, though different writers use a variety of other symbols for the empty string as well, including the lower case Greek letter lambda.
In physics, the permittivity of a medium.
In physics/electronics, the EMF of a circuit
In physics, the strain of a material (A ratio of extensions).
In automata theory, a transition that involves no shifting of an input symbol.
In astronomy, the fifth brightest (usually) star in a constellation. See Bayer designation.
In the International Phonetic Alphabet, the open-mid front unrounded vowel, (but generally written ɛ instead of ε) as in the English word "pet" (/pɛt/)
In astronomy, Epsilon is the name for Uranus' most distant and most visible ring.
In chemistry, the molar extinction coefficient of a chromophore.
In economics, ε refers to elasticity.

[edit] Fictional names

In the popular web series "Red vs. blue", Epsilon is the name of the AI assigned to freelancer Washington.
Epsilon in Malaysian Pale is the name of the second solo album released by Tangerine Dream leader Edgar Froese in 1975.
Epsilon is also an Australian light-powered female-looking robot that fought Pluto in an episode of Astro Boy.
Epsilon Eridani III is the planet that the spacestation Babylon 5 orbited in the eponymous sci-fi television series.
E-104 Epsilon is also the name of a robot in Sonic Adventure.
"Epsilon 9" is the name of the Federation space station consumed by the V'ger cloud in Star Trek: The Motion Picture.
Epsilon is the name of an unlockable creature in the game Monster Rancher 2
In Greek it is used for Epsilon Team.
"Epsilon Mirror" is the name of one of Aika's moves in the video game Skies of Arcadia.
Epsilon is the leader of the Rebellion in Mega Man X: Command Mission
"The Epsilon Program" is a mysterious cult in the video game Grand Theft Auto: San Andreas by Game Developer Rockstar North. This cult is thought to be based on Scientology.
The Epsilon Project is a fictional experiment mentioned in the Dreamcast and Xbox versions of Dead or Alive 2 and is based around cloning.
Epsilon is the lowest of five social castes in the Aldous Huxley novel Brave New World.
"Plan Epsilon" was one of many plans to restore Doctor Doom to life in the event of his death, as shown in Fantastic Four issue no. 246, written by Stan Lee.
Epsilon-Eagle is the name of the protagonist in the Sega Mega Drive game Alien Soldier.
Epsilon was the name given to one of the ground support teams in the Sony Playstation game G-Police
Epsilon is the name of the newly resurrected Yuri Faction in the Yuri's Revenge mod Mental Omega