1. A substance or compound added to a system to cause a chemical reaction or to test for the presence of another substance
The chemist added a reagent to the solution to detect the presence of chlorine.
O químico adicionou um reagente à solução para detectar a presença de cloro.
2. In laboratory settings, any substance used in a chemical analysis or synthesis
Quality control requires testing each batch with standard reagents.
O controle de qualidade requer testar cada lote com reagentes padrão.