Whats the defenition of heat ?

Heat in Physics is an energy that is in a process of transfer between a system and its surroundings other than the transfer of matter. In  Thermodynamics,  a science that deals with the study of heat and temperature and their relationship to energy and work, finer details of the process is unpredictable. Heat flows from a hotter to a colder body when there is a physical pathway. This pathway is suitable and can be direct such as radiation and conduction. It can also be indirect as in convective circulation.

The salt in the sea water dehydrated the sailor because her body could not take in the amount to salt in the sea water