a semiconductor whose resistance will vary with temperature.

(1) a foreign substance mixed with or attached to a given substance for the determination of the location or distribution of the substance. (2) an element or compound that has been made radioactive so that it can be easily followed (traced) in biological and industrial processes. Radiation emitted by the radioisotope pinpoints its location.

usually refers to the percentage reduction of a specific or group of pollutants by a specific wastewater treatment step or treatment plant.

an instrument for measurement of turbidity in which a standard suspension is used for reference.