1. The reduction or the weakening or the concentration of something with a thinner: The recipe called for a dilution of one part concentrate to two parts water.
2. A liquid which has been made thiner, by the addition of another element, such as water: Typically the dilution of frozen juice is done to a specific ratio.

The speed or pace at which populations are made weaker or smaller because of a lack of births and immigration: The annual statistics gathered by the government tracked the dilution rates of the various groups of people.

1. A technique used for measuring the size of a fluid-filled cavity by injecting a very cold sample of known volume and by measuring the change in temperature of the whole, assessing the degree of thermodilution, and hence the total volume of the cavity.
2. A method of cardiac output determination.

A bolus (intravenous injection of a solution) of known volume and temperature is injected into the right atrium, and the resultant change in blood temperature is detected by a thermistor previously placed in the pulmonary artery with a catheter.