a triangular alluvial deposit at the mouth of a river
the fourth letter of the Greek alphabet (Δ, δ), equivalent to and transliterated as roman d
in mathematics, an increment of a variable
deltaic /delʹtayik/ adj
[Middle English deltha from Greek delta, of Semitic origin; related to Hebrew dāleth, fourth letter of the Hebrew alphabet; (sense 1) from the triangular shape of the Greek character]