The correct way to analyse motion in detail to to use a branch of maths called calculus. Calculus deals with the rate of change of one quantity with respect to another. Typically in physics we want to find the rate of change of a quantity with respect to time, often called merely, 'the rate of change' the that quantity. For example, the rate of change of distance is speed. Some examples of rates of change of quantities are shown in the table.
Symbol | Pronounced | Meaning | Example |
| Delta | The change in | A movement of |
| Delta | The small change in | A movement of |
| Delta | The average rate of change of | Average speed |
| Delta | The average rate of change of | Average speed |
| Dee | The instantaneous speed at a time | The speed |
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