1. The symbol $\Delta$ (uppercase Greek letter Delta) is commonly used in mathematics and science to represent a "change" or "difference" in a quantity. 2. For example, if you have a variable $x$, then $\Delta x$ means the change in $x$, which is calculated as the difference between a final value and an initial value: $$\Delta x = x_{final} - x_{initial}$$ 3. This concept is used in many areas such as algebra, calculus, physics, and engineering to denote how much a quantity has changed. 4. In physics, $\Delta t$ often represents a change in time, and $\Delta v$ a change in velocity. 5. Remember, $\Delta$ always indicates a difference or change between two values, not a single value itself.