The term "delta" commonly refers to a landform that forms at the mouth of a river, where it splits into multiple branches before entering a larger body of water, such as an ocean or a lake. This process occurs due to the deposition of sediment carried by the river, which creates a triangular or fan-shaped area of land. In a broader sense, "delta" can also mean a change or difference, particularly in mathematics or science, denoting a difference between two values.
The word "delta" comes from the Greek letter "Δ" (delta), which has a triangular shape similar to the landform created at the mouth of a river.