assay

assay 1 An analysis done to determine the presence and amount of a substance. An assay may be done, for example, to determine the level of thyroid hormones in the blood. 2 An analysis done to determine the biologic or pharmacologic potency of a drug. For example, an assay may be done of a vaccine to determine its potency. 3 As a verb, to try or attempt. For example, “She assayed this operation for the first time and was understandably nervous.” 4 The act of analyzing a mixture for one or more of its components. 5 The act of judging the value or worth of something.