Full width at half maximum

Full width at half maximum (FWHM) is a way of measuring how wide something is. Imagine you have an ice cream cone. FWHM is like measuring how wide the cone is from one wide edge to the other wide edge. In math, it is a way of measuring how wide a peak or 'bump' is on a graph. To find FWHM, you measure how wide the peak is at the middle (half maximum) and then you measure how wide the peak is from one side to the other.