Question

compare a delta and an estuary .

Answer 1

The estuary is like funnel-shaped, the mouth of a river from where the tides move in and out. Conversely, Delta is a triangular land at the river mouth travelled across by its distributaries. Rivers that encounter high tides are more likely to form estuary.

Answer 2

From Estuary and River delta pages on Wikipedia, you'd see that they are two different things entirely. An estuary is a body of water, while a delta is a landmass. Estuaries are places where the river meets the ocean. Deltas are formed by the accumulation of sediments borne by the river.