delta
US /ˈdel.t̬ə/
UK /ˈdel.t̬ə/
1.
the fourth letter of the Greek alphabet (Δ, δ)
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The symbol for delta is a triangle.
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In mathematics, delta often represents a change in a variable.
2.
a triangular tract of sediment deposited at the mouth of a river, typically where it diverges into several outlets
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The Nile Delta is a fertile region in Egypt.
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Many birds nest in the river delta.