Cuneiform

Cuneiform script is one of the earliest known systems of writing. It used wedge-shaped marks on clay tablets, made by a reed stylus. The name cuneiform itself means "wedge shaped", from the Latin cuneus "wedge" and forma "shape". It came into English usage probably from the Old French cunéiforme.

Trilingual cuneiform inscription of Xerxes at Van Fortress in Turkey, written in Old Persian, Akkadian, and Elamite

It is a letter, and the script is cuneiform, the date ~2400 BC

It was first used in Sumer in the late 4th millennium BC (the 'Uruk IV' period). Cuneiform writing began as a system of pictographs. In the third millennium, the signs became simplified and more abstract. Fewer characters were used, from about 1,000 in the early Bronze Age to about 400 in late Bronze Age (Hittite cuneiform). The system used a combination of phonetic, consonantal alphabetic (no vowels) and syllabic signs.

The original Sumerian script was adapted for the writing of the Akkadian, Eblaite, Elamite, Hittite, Luwian, Hattic, Hurrian, and Urartian languages, and it inspired the Ugaritic and Old Persian alphabets. Cuneiform writing was gradually replaced by the Phoenician alphabet during the Neo-Assyrian Empire. By the 2nd century BC, the script was extinct. All knowledge of how to read it was lost until it began to be deciphered in the 19th century.