assay

Word family

• assayer
  nounC2
• bioassay
  nounC2
• immunoassay
  nounC2

Synonym discussion

Sense: noun/1

All four words describe ways of finding out what something is or contains, but they sit at different levels of formality and precision. 'Test' is the everyday word — a doctor runs a blood test, a teacher gives a test. 'Examination' is broader and can be visual; a doctor examines a patient by looking and touching, no chemistry required. 'Analysis' is the general scientific term: it splits something complex into parts to understand it, and applies to data, ideas, or substances. 'Assay' is the narrowest and most technical: it is a specific quantitative laboratory procedure that measures the components or purity of a physical substance, especially metal, ore, or a drug. So a mining company might run an assay on a rock sample, a hospital might use an antibody assay to detect a virus, but you would say 'a blood test', not 'a blood assay', when speaking to a patient.

Common collocations

Etymology

Assay came into Middle English in the 14th century from Old French 'assai' or 'essai', meaning a trial or attempt, which itself goes back to Late Latin 'exagium', a weighing — from the Latin verb 'exigere', to weigh out or examine carefully. The same root produced the related word 'essay' (a written attempt). Over time, English narrowed 'assay' to its technical sense of testing metals and other substances, while 'essay' kept the wider meaning of a trial or composition.