1. (河流在入海处形成的)三角洲
A delta is an area of low, flat land shaped like a triangle, where a river splits and spreads out into several branches before entering the sea.

1. the 4th letter of the Greek alphabet

2. a low triangular area of alluvial deposits where a river divides before entering a larger body of water

e.g. the Mississippi River delta
the Nile delta

3. an object shaped like an equilateral triangle