Fifth letter of the
Greek alphabet, capital Ε and lower-case ε. The lower-case letter has two equally correct variant forms, one like a reversed 3 and the other a 'c' with a middle stroke, like ∈. The HTML codes for it are Ε and ε
In English the name is often pronounced with the stress on the first syllable, as in Epsom, and this is also the accentuation of the Modern Greek. An older English pronunciation stresses the long I, ep-SI-lon as in Simon, in accord with the Latin quantity.
It derives from the Phoenician letter for H, related to Hebrew ה he and Arabic ه ha. The Semitic scripts used only consonant symbols, but the Greeks used some of those they didn't need as vowels, creating the first true alphabet.
The letter was adopted into the Roman alphabet via Etruscan as E, and into the Cyrillic alphabet as the same shape Е.
In Ancient Greek it had the pronunciation of E in bet, when short, and in Modern Greek it has kept this sound. The ancient diphthong αι AI also has this E sound in Modern Greek. There is no distinction of vowel length in Modern, but in Ancient Greek Ε was originally used as a long vowel also; in fact two distinct long vowels. In around 400 BCE a spelling reform was introduced in Athens. They shifted to a system already used by the Ionian Greeks, using the combination ΕΙ for a long mid-close vowel (as in German Seele) and Η eta for a long mid-open vowel (German Bär), leaving plain epsilon for the short vowel.
The original name of the letter was just ei (that is, just e before the reform). Then it became e psilon 'bare E' to distinguish it from the letter eta, which until then they had used as an aspirate: see also psilosis.