Ε

Epsilon in a capital letter Etymologicum Magnum (1499).

Epsilon (uppercase Ε, lowercase ε [variant ε ]; called in ancient Greek εἶ eî /êː/, Modern Greek έψιλον epsilon /ˈe.psi.lon/, lit. 'e simple') is the fifth letter of the Greek alphabet.

In the Greek numeral system it has a value of 5 (Ε΄).

History

Epsilon evolved from the letter he (𐤄) of the Phoenician alphabet, from which also comes the Hebrew he ה and the Arabic ḥā ه'. The letter was originally a consonant, but in Greek it evolved into a vowel in classical times.

In the oldest inscriptions this letter appears as its Phoenician model, that is, a mirror image of the current one with its three "arms" pointing to the left. Later, the letter returned to its current position. Epsilon was used in all local Greek alphabets, and its shape was relatively similar in most alphabets, except for direction and slant. However, in some alphabets (for example Corinthian or Epirus) epsilon can resemble the letter B and in others (for example Sicyon) an hourglass.

Epigraphic variants

In archaic epigraphic sources the following variants appear:

Use

• In the Greek numeration system it has a value of 5 (ε).

• In mathematics, ε usually designate small quantities, or amounts that tend to zero, particularly in the study of limits or continuity.
• In physics, it is used to represent the value of dielectric constant.
• Mistakes of all kinds in the study of sciences in general.
• In automatons and formal languages, it represents the empty word.
• In Mathematics it is used to designate the neighborhood or environment of a set.
• In chemistry it is used to refer to the extinction coefficient of a dissolution.

Unicode

• Greek

• Copt

• Latino

• Maths