A chemical reaction in which at least one of the reactants is a solid. Solid-state reactions can be classified into five types:

1. (1) solid → products,

2. (2) solid + gas → products,

3. (3) solid + liquid → products,

4. (4) solid + solid → products, and

5. (5) reactions at the surface of a solid.

The arrangement of atoms in the solid is an important aspect of a solid-state reaction.