Ayin or ʿayin (Hebrew: [ajin], Arabic: [ʕajn]^{[see below]}) is the sixteenth letter in many Semitic abjads, including Phoenician, Aramaic, Hebrew ע and Arabic ʿayn ع (in abjadi order). It is the twenty-first letter in the new Persian alphabet (similar to an o but silent). It represents a sound like a voiced pharyngeal fricative (/ʕ/), which has no equivalent in English.

There are many possible transliterations, most commonly ʿ, U+02BF ʿ modifier letter left half ring (HTML: ʿ). For details, see section Transliteration.

The Phoenician letter gave rise to the Greek Omicron (Ο), the Latin O, and Cyrillic (О), all representing vowels.

The sound represented by ayin is common to much of the Afrasiatic language family, such as the Egyptian, Cushitic, and Semitic languages. Some scholars believe that the sound in Proto-Indo-European transcribed h₃ was similar, though this is debatable. (See Laryngeal theory#Pronunciation.)

ʿAyin is usually transliterated into the Latin alphabet with ʿ, (U+02BF) "modifier letter left half ring" (in the Spacing Modifier Letters range). This is true in ALA-LC romanization of Arabic. This symbol originated from Semitic romanization and Egyptological transliteration, where it was inspired by the Greek spiritus asper. Example: The name of the letter itself, ʿayin.

Neşet Ertaş (born 1938 in Çiçekdağı, Kırşehir) is a Turkish folk music singer, lyrics writer and a virtuoso of the traditional Turkish instrument bağlama. His profession in Turkish is known as halk şairi, which literally means "folk poet".

He was born in 1938, in Kırtıllar, a village in Kırşehir to his father Muharrem Ertaş, also a halk şairi, and his mother Döne Koç. Neşet Ertaş went to primary school for only 2 years, Before this he used to play the violin then the saz (the Turkish national instrument, baglama).

Neşet Ertaş interprets musical pieces of the Abdal tradition, following his father. With his forceful saz, his warm voice pure and simple language has Neşet Ertaş in a short time gathered people from Central Anatolia then the whole of Turkey.