A hypsometric curve is an empirical cumulative distribution function of elevations in a catchment

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

. Differences in hypsometric curves between landscapes arise because the geomorphic

Geomorphology

Geomorphology is the scientific study of landforms and the processes that shape them...

 processes that shape the landscape may be different.
The hypsometric curve may also be shown as a continuous function and graphically displayed as an x-y plot with elevation on the vertical, y-axis and area above the corresponding elevation on the horizontal or x-axis. The curve can also be shown in non-dimensional or standardized form by scaling elevation and area by the maximum values. The non-dimensional hypsometric curve provides hydrologist and geomorphologist with a way to assess the similarity of watersheds

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

— and is one of several characteristics used for doing so.