Reactant

In chemistry, reactant is the term for the ingredients for a chemical reaction.^[1] Reactants are changed into products by the reaction, and are written on the left side of a chemical equation. The words "reactant" and "reagent" are often used to mean the same things, even though they are formally different.

For example, carbon dioxide and water are the reagents in photosynthesis:

6 CO₂ + 6 H₂O → C₆H₁₂O₆ + 6 O₂

Glucose and oxygen are the products.

Catalysts and solvents are not reactants because they are not used up, even if they are part of the reaction mechanism.