That pressure of a gas in a liquid, which is in equilibrium with the solution. In a mixture of gases, the partial pressure of any one gas is the total pressure times the fraction of the gas in the mixture (by volume or number of molecules). For this reason, the aggregate quantity of partial pressures in the mixture is the equivalent of its total pressure. Partial pressure has much significance in determining the flows of its gases, which is important since gases have a tendency in equalizing the pressure between two areas that are connected.