1. To modify temperatures so they can be applied when necessary: James thermalizes the heat in his residence during the winter so he and his family can live in warm conditions and not get too cold.
2. To achieve a heat equilibrium with the environment: A substance, as with water, is used to slow down, lessen, or thermalize the velocity of the fast neutrons in a nuclear reactor and therefore intensify the probability of fission, or of the splitting of the massive nucleus into tinier nuclei.