A type of hygrometer that measures the water vapor content of the atmosphere by means of the absorption of vapor by a hygroscopic chemical. The amount of vapor absorbed may be determined in an absolute manner by weighing the hygroscopic material (see gravimetric hygrometry), or in a nonabsolute manner by measuring a physical property of the substance that varies with the amount of water vapor absorbed. The humidity strip, the carbon-film hygrometer element, and the thin-film capacitor are examples of the latter.