In chemistry, a suspension is a liquid (or gas) medium in which small solid (or liquid) particles are uniformly dispersed, and in which settlement is hindered by intermolecular collisions and by the fluid's viscosity. Examples of suspensions are dust in air, and fine particles of sand in water. The particles are larger than those found in a colloid and will settle if the suspension stands undisturbed.

In geology, the meaning is similar: 'suspension' is this case, though, referring generally to the manner in which small sedimentary particles are carried along by rivers. Turbulence and upward eddies keep particles suspended and make the water look muddy. Worldwide, the amount of material transported in this way is tremendous, estimated at 80 metric tons of solids per square km of the Earth's surface every year.