Epsilon
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Epsilon (uppercase Ε, lowercase ε or lunate ϵ; Greek: έψιλον) is the fifth letter of the Greek alphabet, corresponding phonetically to a mid front unrounded vowel /e/. In the system of Greek numerals it also has the value five. It was derived from the Phoenician letter He
The name of the letter was originally εἶ (Ancient Greek: [êː]), but the name was changed to ἒ ψιλόν (e psilon "simple e") in the Middle Ages to distinguish the letter from the digraph αι, a former diphthong that had come to be pronounced the same as epsilon.
In essence, the uppercase form of epsilon looks identical to Latin E. The lowercase version has two typographical variants, both inherited from medieval Greek handwriting. One, the most common in modern typography and inherited from medieval minuscule, looks like a reversed "3". The other, also known as lunate or uncial epsilon and inherited from earlier uncial writing,[1][2] looks like a semicircle crossed by a horizontal bar. While in normal typography these are just alternative font variants, they may have different meanings as mathematical symbols. Computer systems therefore offer distinct encodings for them.[1] In Unicode, the character U+03F5 "Greek lunate epsilon symbol" (ϵ) is provided specifically for the lunate form. In TeX, \epsilon
(
) denotes the lunate form, while \varepsilon
(
) denotes the reversed-3 form.
There is also a Latin epsilon or "open e", which looks similar to the Greek lowercase epsilon. It is encoded in Unicode as U+025B ("Latin small-letter open e", ɛ) and U+0190 ("Latin capital-letter open e", Ɛ) and is used as an IPA phonetic symbol. The lunate or uncial epsilon has also provided inspiration for the euro sign (€).
The lunate epsilon (ϵ) is not to be confused with the set membership symbol (∈); nor should the Latin uppercase epsilon (Ɛ) be confused with the Greek uppercase sigma (Σ). The symbol , first used in set theory and logic by Giuseppe Peano and now used in mathematics in general for set membership ("belongs to") did, however, evolve from the letter epsilon, since the symbol was originally used as an abbreviation for the Latin word "est". In addition, mathematicians often read the symbol as "element of", as in "1 is an element of the natural numbers" for , for example. As late as 1960, itself was used for set membership, while its negation "does not belong to" (now ) was denoted by (epsilon prime).[3] Only gradually did a fully separate, stylized symbol take the place of epsilon in this role. In a related context, Peano also introduced the use of a backwards epsilon, , for the phrase "such that", although the abbreviation "s.t." is occasionally used in place of in informal writing.
History
Origin
The letter Ε was taken over from the Phoenician letter He (
Sound value
While the original pronunciation of the Phoenician letter He was [h], the earliest Greek sound value of Ε was determined by the vowel occurring in the Phoenician letter name, which made it a natural choice for being reinterpreted from a consonant symbol to a vowel symbol denoting an [e] sound.[5] Besides its classical Greek sound value, the short /e/ phoneme, it could initially also be used for other [e]-like sounds. For instance, in early Attic before c.500 B.C., it was used also both for the long, open /ɛː/, and for the long close /eː/. In the former role, it was later replaced in the classic Greek alphabet by Eta (Η), which was taken over from eastern Ionic alphabets, while in the latter role it was replaced by the digraph spelling ΕΙ.
Epichoric alphabets
Some dialects used yet other ways of distinguishing between various e-like sounds.
In Corinth, the normal function of Ε to denote /e/ and /ɛː/ was taken by a glyph resembling a pointed B (
In Sicyon, a variant glyph resembling an X (
In Thespiai (Boeotia), a special letter form consisting of a vertical stem with a single rightward-pointing horizontal bar (
Glyph variants
After the establishment of the canonical classic Greek alphabet, new glyph variants for Ε were introduced through handwriting. In the uncial script (used for literary papyrus manuscripts in late antiquity and then in early medieval vellum codices), the "lunate" shape (
Uncial | Uncial variants | Cursive variants | Minuscule | Minuscule with ligatures |
---|---|---|---|---|
Uses
International Phonetic Alphabet
Despite its pronunciation as mid, in the International Phonetic Alphabet, the Latin epsilon /ɛ/ represents open-mid front unrounded vowel, as in the English word pet /pɛt/.
Symbol
The uppercase Epsilon is not commonly used outside of the Greek language because of its similarity to the Latin letter E.
The Greek lowercase epsilon ε, the lunate epsilon symbol ϵ, or the Latin lowercase epsilon ɛ (see above) is used as the symbol for:
- In mathematics (particularly calculus), an arbitrarily small positive quantity is commonly denoted ε; see (ε, δ)-definition of limit.
- In reference to this, the late mathematician Paul Erdős also used the term "epsilons" to refer to children (Hoffman 1998, p. 4).
- In mathematics, Hilbert introduced epsilon terms as an extension to first order logic; see epsilon calculus.
- 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 epsilon numbers are ordinal numbers that satisfy the fixed point ε = ωε. The first epsilon number, ε0, is the limit ordinal of the set {ω, ωω, ωωω, ...}.
- In computer science, the empty string, though different writers use a variety of other symbols for the empty string as well, usually the lower-case Greek letter lambda (λ).
- In computer science, the machine epsilon, the upper bound on the relative error due to rounding in floating point arithmetic.
- In physics, the permittivity of a medium; with the subscript 0 (ϵ0), the permittivity of free space.
- 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 star in a constellation (see Bayer designation).
- In astronomy, Epsilon is the name for Uranus' most distant and most visible ring.
- In planetary science, ε is the denotion of axial tilt.
- In chemistry, the molar extinction coefficient of a chromophore.
- In economics, ε refers to elasticity.
- In statistics, to refer to error terms.
- In statistics, to refer to the degree of sphericity in repeated measures ANOVAs.
- In agronomy, to represent the "photosynthetic efficiency" of a particular plant or crop.
Unicode
- Greek Epsilon
Character | Ε | ε | ϵ | ϶ | ||||
---|---|---|---|---|---|---|---|---|
Unicode name | GREEK CAPITAL LETTER EPSILON | GREEK SMALL LETTER EPSILON | GREEK LUNATE EPSILON SYMBOL | GREEK REVERSED LUNATE EPSILON SYMBOL | ||||
Encodings | decimal | hex | decimal | hex | decimal | hex | decimal | hex |
Unicode | 917 | U+0395 | 949 | U+03B5 | 1013 | U+03F5 | 1014 | U+03F6 |
UTF-8 | 206 149 | CE 95 | 206 181 | CE B5 | 207 181 | CF B5 | 207 182 | CF B6 |
Numeric character reference | Ε | Ε | ε | ε | ϵ | ϵ | ϶ | ϶ |
Named character reference | Ε | ε | ||||||
DOS Greek | 132 | 84 | 156 | 9C | ||||
DOS Greek-2 | 168 | A8 | 222 | DE | ||||
Windows 1253 | 197 | C5 | 229 | E5 | ||||
TeX | \varepsilon | \epsilon |
- Coptic Eie
Character | Ⲉ | ⲉ | ||
---|---|---|---|---|
Unicode name | COPTIC CAPITAL LETTER EIE | COPTIC SMALL LETTER EIE | ||
Encodings | decimal | hex | decimal | hex |
Unicode | 11400 | U+2C88 | 11401 | U+2C89 |
UTF-8 | 226 178 136 | E2 B2 88 | 226 178 137 | E2 B2 89 |
Numeric character reference | Ⲉ | Ⲉ | ⲉ | ⲉ |
- Latin Open E
Character | Ɛ | ɛ | ᶓ | ᵋ | ||||
---|---|---|---|---|---|---|---|---|
Unicode name | LATIN CAPITAL LETTER OPEN E | LATIN SMALL LETTER OPEN E | LATIN SMALL LETTER OPEN E WITH RETROFLEX HOOK | MODIFIER LETTER SMALL OPEN E | ||||
Encodings | decimal | hex | decimal | hex | decimal | hex | decimal | hex |
Unicode | 400 | U+0190 | 603 | U+025B | 7571 | U+1D93 | 7499 | U+1D4B |
UTF-8 | 198 144 | C6 90 | 201 155 | C9 9B | 225 182 147 | E1 B6 93 | 225 181 139 | E1 B5 8B |
Numeric character reference | Ɛ | Ɛ | ɛ | ɛ | ᶓ | ᶓ | ᵋ | ᵋ |
Character | ɜ | ɝ | ᶔ | ᶟ | ||||
---|---|---|---|---|---|---|---|---|
Unicode name | LATIN SMALL LETTER REVERSED OPEN E | LATIN SMALL LETTER REVERSED OPEN E WITH HOOK | LATIN SMALL LETTER REVERSED OPEN E WITH RETROFLEX HOOK | MODIFIER LETTER SMALL REVERSED OPEN E | ||||
Encodings | decimal | hex | decimal | hex | decimal | hex | decimal | hex |
Unicode | 604 | U+025C | 605 | U+025D | 7572 | U+1D94 | 7583 | U+1D9F |
UTF-8 | 201 156 | C9 9C | 201 157 | C9 9D | 225 182 148 | E1 B6 94 | 225 182 159 | E1 B6 9F |
Numeric character reference | ɜ | ɜ | ɝ | ɝ | ᶔ | ᶔ | ᶟ | ᶟ |
Character | ᴈ | ᵌ | ʚ | ɞ | ||||
---|---|---|---|---|---|---|---|---|
Unicode name | LATIN SMALL LETTER TURNED OPEN E | MODIFIER LETTER SMALL TURNED OPEN E | LATIN SMALL LETTER CLOSED OPEN E | LATIN SMALL LETTER CLOSED REVERSED OPEN E | ||||
Encodings | decimal | hex | decimal | hex | decimal | hex | decimal | hex |
Unicode | 7432 | U+1D08 | 7500 | U+1D4C | 666 | U+029A | 606 | U+025E |
UTF-8 | 225 180 136 | E1 B4 88 | 225 181 140 | E1 B5 8C | 202 154 | CA 9A | 201 158 | C9 9E |
Numeric character reference | ᴈ | ᴈ | ᵌ | ᵌ | ʚ | ʚ | ɞ | ɞ |
- Mathematical Epsilon
Character | 𝚬 | 𝛆 | 𝛦 | 𝜀 | 𝜠 | 𝜺 | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Unicode name | MATHEMATICAL BOLD CAPITAL EPSILON | MATHEMATICAL BOLD SMALL EPSILON | MATHEMATICAL ITALIC CAPITAL EPSILON | MATHEMATICAL ITALIC SMALL EPSILON | MATHEMATICAL BOLD ITALIC CAPITAL EPSILON | MATHEMATICAL BOLD ITALIC SMALL EPSILON | ||||||
Encodings | decimal | hex | decimal | hex | decimal | hex | decimal | hex | decimal | hex | decimal | hex |
Unicode | 120492 | U+1D6AC | 120518 | U+1D6C6 | 120550 | U+1D6E6 | 120576 | U+1D700 | 120608 | U+1D720 | 120634 | U+1D73A |
UTF-8 | 240 157 154 172 | F0 9D 9A AC | 240 157 155 134 | F0 9D 9B 86 | 240 157 155 166 | F0 9D 9B A6 | 240 157 156 128 | F0 9D 9C 80 | 240 157 156 160 | F0 9D 9C A0 | 240 157 156 186 | F0 9D 9C BA |
UTF-16 | 55349 57004 | D835 DEAC | 55349 57030 | D835 DEC6 | 55349 57062 | D835 DEE6 | 55349 57088 | D835 DF00 | 55349 57120 | D835 DF20 | 55349 57146 | D835 DF3A |
Numeric character reference | 𝚬 | 𝚬 | 𝛆 | 𝛆 | 𝛦 | 𝛦 | 𝜀 | 𝜀 | 𝜠 | 𝜠 | 𝜺 | 𝜺 |
Character | 𝝚 | 𝝴 | 𝞔 | 𝞮 | ||||
---|---|---|---|---|---|---|---|---|
Unicode name | MATHEMATICAL SANS-SERIF BOLD CAPITAL EPSILON | MATHEMATICAL SANS-SERIF BOLD SMALL EPSILON | MATHEMATICAL SANS-SERIF BOLD ITALIC CAPITAL EPSILON | MATHEMATICAL SANS-SERIF BOLD ITALIC SMALL EPSILON | ||||
Encodings | decimal | hex | decimal | hex | decimal | hex | decimal | hex |
Unicode | 120666 | U+1D75A | 120692 | U+1D774 | 120724 | U+1D794 | 120750 | U+1D7AE |
UTF-8 | 240 157 157 154 | F0 9D 9D 9A | 240 157 157 180 | F0 9D 9D B4 | 240 157 158 148 | F0 9D 9E 94 | 240 157 158 174 | F0 9D 9E AE |
UTF-16 | 55349 57178 | D835 DF5A | 55349 57204 | D835 DF74 | 55349 57236 | D835 DF94 | 55349 57262 | D835 DFAE |
Numeric character reference | 𝝚 | 𝝚 | 𝝴 | 𝝴 | 𝞔 | 𝞔 | 𝞮 | 𝞮 |
Character | ∈ | ∊ | ∋ | ∉ | ||||
---|---|---|---|---|---|---|---|---|
Unicode name | ELEMENT OF | SMALL ELEMENT OF | CONTAINS AS MEMBER | NOT AN ELEMENT OF | ||||
Encodings | decimal | hex | decimal | hex | decimal | hex | decimal | hex |
Unicode | 8712 | U+2208 | 8714 | U+220A | 8715 | U+220B | 8713 | U+2209 |
UTF-8 | 226 136 136 | E2 88 88 | 226 136 138 | E2 88 8A | 226 136 139 | E2 88 8B | 226 136 137 | E2 88 89 |
Numeric character reference | ∈ | ∈ | ∊ | ∊ | ∋ | ∋ | ∉ | ∉ |
Named character reference | ∈ | ∋ | ∉ |
These characters are used only as mathematical symbols. Stylized Greek text should be encoded using the normal Greek letters, with markup and formatting to indicate text style.
Initial
- folio 64 verso
- folio 125 verso
References
- 1 2 Nick Nicholas: Letters, 2003–2008. (Greek Unicode Issues)
- ↑ Colwell, Ernest C. (1969). "A chronology for the letters Ε, Η, Λ, Π in the Byzantine minuscule book hand". Studies in methodology in textual criticism of the New Testament. Leiden: Brill. p. 127.
- ↑ Halmos, Paul R. (1960). Naive Set Theory. New York: Van Nostrand. pp. 5–6. ISBN 978-1614271314.
- ↑ Jeffery, Lilian H. (1961). The local scripts of archaic Greece. Oxford: Clarendon. pp. 63–64.
- ↑ Jeffery, Local scripts, p.24.
- ↑ Jeffery, Local scripts, p.114.
- ↑ Jeffery, Local scripts, p.138.
- ↑ Nicholas, Nick (2005). "Proposal to add Greek epigraphical letters to the UCS" (PDF). Archived from the original (PDF) on 2006-05-05. Retrieved 2010-08-12.
- ↑ Jeffery, Local scripts, p.89.
- ↑ Thompson, Edward M. (1911). An introduction to Greek and Latin palaeography. Oxford: Clarendon. pp. 191–194.
Further reading
Look up Ε or ɛ in Wiktionary, the free dictionary. |
- Hoffman, Paul; The Man Who Loved Only Numbers. Hyperion, 1998. ISBN 0-7868-6362-5.