From the Greek benthos - depth, the bottom of a body of water, inhabited by microorganisms, plants and animals living on the surface or in the soil column. The aggregate of organisms inhabiting the benthos is called the benthal. The benthos is the opposite of the pelagic.

In marine and freshwater waters, the benthos is divided into different vertical zones: the littoral (tidal zone);

sublittoral (up to 200 m), the lower part of which is sometimes distinguished as a special zone - elittoral;

bathyal (up to 2,500-3,000 m)

abyssal (up to 6,000 m);

ultra-abyssal or hadal (deeper than 6000 m);

The depths between these zones are referred to as transitional horizons.