1. Qualitative or quantitative analysis of a substance: The use of an assay refers especially to the test of an ore or drug in order to determine its components and to be so analyzed.
2. A written document of the results of the examination of the components of a matter: Dr. Thompson wanted to read the assay that his students prepared in the lab.

To examine by trial or experiment; to put to a test: The scientist assayed the metal with the intention of determining its specific components.