The five ways in which heat is transferred away from the body

 Conduction:

Direct transfer of heat by contact with a cooler object - conduction of heat to the cooler object

Convection:

Cool air moving across the surface of the body, heat transferred to the cool air, warming it and cooling the body

Radiation:

Heat radiated outward from the warm body to the cooler environment

Evaporation:

The loss of heat through the process of removing water from the surface of the body through vaporization

Respiration:

Inspired air raised to body temperature and then exhaled

Each of these causes of heat loss can play a large or small role in the development of hypothermia, depending on clothing, head cover, wind, weather, etc.