delta

1. the fourth letter of the Greek alphabet ( Δ, δ ), transliterated as ‘d’.
2. a code word representing the letter D, used in radio communication.
3. a difference between two things or values.

   there's a delta between perception and reality

   as long as the price delta is not too great, consumers can be sold on specs and future-proofing

1. variation of a variable or function.
2. a finite increment.
3. the discriminant of a quadratic equation.
4. declination.

Greek, from Phoenician daleth .

1. a triangular tract of sediment deposited at the mouth of a river, typically where it diverges into several outlets.

   the Nile delta

   a huge delta system developed

mid 16th century: originally specifically as the Delta (of the River Nile), from the shape of the Greek letter (see delta¹).