* Part of a proper noun:
* "Thermal Springs Resort"
* "The Thermal Power Plant"
* Used as the first word in a sentence:
* "Thermal energy is a form of energy."
* Used in a title:
* "Thermal Imaging in Medical Diagnosis"
It should not be capitalized when used as a general adjective:
* "The thermal conductivity of copper is high."
* "They used a thermal camera to detect heat."