# Reading a graph

Authored explanation; editorial review pending.

The horizontal axis (abscissa) typically shows the independent variable, like position x or elapsed time t. The vertical axis (ordinate) shows the quantity that depends on it, like particle count or probability density p(x).

A flat horizontal line means the quantity does not change across the axis. A rising curve has positive slope (increasing rate), while a symmetric bell-shaped curve shows high concentration in the centre with tails tapering toward zero on both sides.

## Worked example

1. Plot particle positions −3, −1, +1, +3 along the horizontal axis with a vertical bar for particle count.
2. The graph shows symmetric spread centered at zero.
3. The average position is 0, but the points are visibly separated from the origin.

Check axis labels, units, and whether the curve represents a count, a density, or an accumulated total.