The density of seawater controls much of the movement of water, or the thermohaline flow, in the ocean. The density of seawater is primarily determined by the temperature and salinity of that water. Changes in these two main parameters, potential temperature Θ and salinity S, are multiplied with their thermal expansion α α or haline contraction coefficient β β equal to each other; α α d Θ Θ and β β d S are both proportional to a change in density and are both terms of the linearized equation of state of the ocean (TEOS-10). This similarity is supposed to be relevant for understanding the consequences of sea water mixing.