Answer:
A few definitions:
1. A river delta is a land-form created by deposition of sediment that is carried by a river as the flow leaves its mouth and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or another river that cannot carry away the supplied sediment.
2. The fourth letter of the Greek alphabet ( Δ, δ ), transliterated as ‘d’.
3. a code word representing the letter D, used in radio communication, mostly in the military
4. variation of a variable or function.
5. a finite increment.
This is not a plagiarized passage this is my knowledge and research.