What is the definition of delta?
The answer depends on the context.
Delta is a letter of the Greek alphabet and is shaped like a triangle. Mouths of rivers, which are often triangular in shape are, therefore, also called deltas.
In mathematics, delta is often used to denote a change, particularly a small change.
There is also the Dirac delta function which is an asymptotic spike function and is used in quantum physics.
A river delta is an extension of a river's mouth, where the faster flowing water from a river, suddenly slows when it reaches an open body of water (e.g. a lake) and so deposits the suspended sediments in a zone around the mouth, causing an elevated river bar. Often you can see these from satellite images (google 'Indus River Delta') and is clearly identifiable as an elevation near the mouth of a river. This raised…