选择一个数学符号并给出解释。

Δ
Δ is the uppercase Greek letter delta, which represents the symbol for "change" or "difference". It is commonly used in mathematics and science to represent the difference between two values or as a symbol for a change or variation. In calculus, for example, Δx represents the change in x, which is used to calculate the derivative. It is also used in geometry to represent a triangular shape.