Delta (letter)
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Delta (/ˈdɛltə/ ⓘ DEL-tə; uppercase Δ, lowercase δ; Greek: δέλτα, délta, [ˈðelta]) is the fourth letter of the Greek alphabet. In the system of Greek numerals, it has a value of four. It was derived from the Phoenician letter dalet 𐤃. Letters that come from delta include the Latin D and the Cyrillic Д.
A river delta (originally, the delta of the Nile River) is named so because its shape approximates the triangular uppercase letter delta. Contrary to a popular legend, this use of the word delta was not coined by Herodotus.