The starting material in a chemical reaction is called a reactant.

Reactants are the substances that are present at the beginning of a chemical reaction and undergo a chemical change to form new substances called products.

Here's a simple example:

* Reactants: Hydrogen (H₂) and Oxygen (O₂)

* Reaction: Burning of hydrogen gas

* Product: Water (H₂O)

The chemical equation for this reaction is:

2H₂ + O₂ → 2H₂O