Change (Δ)
Elementary
Think of a quantity that goes up or down, like the temperature during a day. The change in the quantity is how much it went up or down: its final value minus its starting value.
High school
Consider a quantity $x$ with an initial value and a final value. The change in $x$ is the final value minus the initial value:
\[\Delta x = x_{\text{final}} - x_{\text{initial}}.\]It is negative when the quantity decreases.
Examples
Examples
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A temperature that goes from $20$ to $15$ degrees
Elementary
The change in temperature is $\Delta T = 15 - 20 = -5$ degrees, the end value minus the start value.
Distinctions involving this term
- Types of difference: Many quantities compare two things by “how far apart” they are. A difference is the result of subtraction and can be negative. No distance is negative. An error compares an approximation with the truth, a change compares the end with the start, and a set difference removes elements.