The space provided above the resin bed in an ion-exchange column to allow for expansion of the bed during backwashing.

In a fluidized-bed reactor, the space between the top of the reaction bed and the top of the reactor.

The height between normal water level and the crest of a dam or the top of a flume.

The vertical distance in a water tank between the maximum water level and the top of the tank.

The vertical distance from the intersection of the top of the freeboard deck amidships with the outer surface of the side plating to the upper edge of the summer load line, or in general terms, the distance from the waterline to the deck.