Eta


Eta is the seventh letter of the Greek alphabet. Originally denoting a consonant /h/, its sound value in the classical Attic dialect of Ancient Greek was a long vowel Open-mid front unrounded vowel|, raised to in hellenistic Greek, a process known as iotacism.
In the ancient Attic number system, the number 100 was represented by "", because it was the initial of ΗΕΚΑΤΟΝ, the ancient spelling of ἑκατόν = "one hundred". In the latter system of Greek numerals it has a value of 8.
Eta was derived from the Phoenician letter heth. Letters that arose from eta include the Latin H and the Cyrillic letter И.

History

Consonant h

The letter shape 'H' was originally used in most Greek dialects to represent the sound /h/, a voiceless glottal fricative. In this function, it was borrowed in the 8th century BC by the Etruscan and other Old Italic alphabets, which were based on the Euboean form of the Greek alphabet. This also gave rise to the Latin alphabet with its letter H.
Other regional variants of the Greek alphabet, in dialects that still preserved the sound /h/, employed various glyph shapes for consonantal heta side by side with the new vocalic eta for some time.
In the southern Italian colonies of Heracleia and Tarentum, the letter shape was reduced to a "half-heta" lacking the right vertical stem. From this sign later developed the sign for rough breathing or spiritus asper, which brought back the marking of the /h/ sound into the standardized post-classical orthography.
Dionysius Thrax in the second century BC records that the letter name was still pronounced heta, correctly explaining this irregularity by stating "in the old days the letter Η served to stand for the rough breathing, as it still does with the Romans."

Long e

In the East Ionic dialect, however, the sound /h/ disappeared by the sixth century BC, and the letter was re-used initially to represent a development of a long vowel, which later merged in East Ionic with instead. In 403 BC, Athens took over the Ionian spelling system and with it the vocalic use of H. This later became the standard orthography in all of Greece.

Itacism

During the time of post-classical Koiné Greek, the sound represented by eta was raised and merged with several other formerly distinct vowels, a phenomenon called iotacism or itacism, after the new pronunciation of the letter name as ita instead of eta.
Itacism is continued into Modern Greek, where the letter name is pronounced and represents the sound /i/. It shares this function with several other letters and digraphs, which are all pronounced alike. This phenomenon at large is called iotacism.

Cyrillic script

Eta was also borrowed with the sound value of into the Cyrillic script, where it gave rise to the Cyrillic letter И.

Uses

Letter

In Modern Greek, due to iotacism, the letter represents a close front unrounded vowel,. In Classical Greek, it represented a long open-mid front unrounded vowel,.

Symbol

Upper case

The uppercase letter Η is used as a symbol in textual criticism for the Alexandrian text-type.
In chemistry, the letter H as symbol of enthalpy sometimes is said to be a Greek eta, but since enthalpy comes from ἐνθάλπος, which begins in a smooth breathing and epsilon, it is more likely a Latin H for 'heat'.
In information theory the uppercase Greek letter H is used to represent the concept of entropy of a discrete random variable.

Lower case

The lowercase letter η is used as a symbol in:
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.