Weight-for-height is an index comparing a child’s weight with the average weight of healthy children of the same height — the standard measure of wasting, or acute thinness. Unlike weight-for-age, it is independent of the child’s age, which makes it practical where birth dates are uncertain. A low weight-for-height means the child is too thin for their frame: the sign of recent food shortage, illness, or both, and the criterion for diagnosing moderate and severe acute malnutrition in emergencies. Feeding programmes use it to admit children for treatment and to track recovery. Because it responds quickly to refeeding, it is also the index that shows whether an intervention is working.