/ ˈdeltə; NAmE / noun
the fourth letter of the Greek alphabet (Δ, δ)
an area of land, shaped like a triangle, where a river has split into several smaller rivers before entering the sea :
the Nile Delta
sense 1 Greek , from Phoenician daleth .
sense 2 mid 16th cent.: originally specifically as the Delta (of the River Nile), from the shape of the Greek letter.