Cuneiform is a system of writing that uses wedge-shaped marks on clay tablets. It was developed by the Sumerians in ancient Mesopotamia (modern-day Iraq) in the 4th millennium BC. Cuneiform was used to write a variety of languages, including Sumerian, Akkadian, Elamite, and Old Persian. It was eventually replaced by alphabetic scripts, but it remained in use for some specialized purposes until the 1st century AD.