(1) An alluvial deposit usually triangular at the mouth of a river of other stream. It is normally built up only where there is no tidal or current action capable of removing the sediment as fast as it is deposited and hence the delta builds forward from the coastline.

(2) A tidal delta is a similar deposit at the mouth of a tidal inlet put there by tidal currents.

(3) A wave delta is a deposit made by large waves which run over the top of a spit or barrier beach and down the landward side.

Image Source: Jacques Descloitres, MODIS Rapid Response Team, NASA/sh - http://visibleearth.nasa.gov/view_rec.php?id=4927