DELTA

[del.ta] n [ME deltha, fr. Gk delta, of Sem origin; akin to Heb daleth daleth] (13c) 1: the 4th letter of the Greek alphabet

2: something shaped like a capital Greek delta; esp: the alluvial deposit at the mouth of a river

3: an increment of a variable-usu.symbolized in math contexts by a capital Greek delta -- del.ta.ic adj

[2]delta adj (ca. 1929): fourth in position in the structure of an organic molecule from a particular group or atom Delta (1952)--a communications code word for the letter d