What does reagent mean?
Reagent is a specialist term for a substance used to bring about a chemical reaction or to make the presence of another substance detectable. In an ordinary chemical reaction, a reagent may supply one of the substances that combine, or it may act as a catalyst that facilitates the process without being consumed. In laboratories, reagents are also used in diagnostic and analytical tests, where a colour change, precipitate, or other visible effect reveals the presence or concentration of a target material. The term is therefore broader than its everyday associations with test tubes and laboratory glassware might suggest. It is related to the words reaction and reactive, reflecting the idea of a substance that acts or responds. Reagent is most often encountered in chemistry, biology, medicine, and industrial processes, but it can also describe a substance intentionally introduced to produce a desired response in another material.
nounA reagent is a substance used to cause a chemical reaction or to detect, identify, or measure another substance in a laboratory test. In chemistry, it may participate in the reaction or enable it.
- A substance used to cause or enable a chemical reaction.
- A laboratory substance used to detect, identify, or measure another substance, especially in analytical or diagnostic testing.
"The technician added a colorless reagent to the solution, causing it to turn blue."
"The technician added a colorless reagent to the solution, causing it to turn blue."
"The blood sample was tested with a reagent that changes color when the target substance is present."
The standard plural is reagents.
"The laboratory stores dangerous reagents in designated cabinets."
A reagent is a chemical matchmaker: add it, and a hidden reaction becomes visible.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does reagent come from?
English borrowed reagent from French réactif in the early nineteenth century. The French word was based on Latin reagere, formed from re- and agere, meaning “to do,” “act,” or “drive,” and conveying the idea of acting back or responding. The same Latin root underlies reaction, react, reactive, and agent, reflecting the close connection between a reagent and the reactions in which it participates.
Related word forms
How reagent is actually used
Reagent is primarily a formal scientific term used in chemistry, biology, medicine, and laboratory analysis. Outside technical contexts, it may sound unusual or deliberately precise.
Easily confused with reagent
A reagent is a substance intentionally added to cause or reveal a reaction, whereas a reactant is any participant consumed or formed during that reaction.