(1) The act or the process of producing and excreting a watery, saline fluid that evaporates from the skin
(2) The fluid itself that is excreted by the body and evaporates immediately and thereby serves as a means to regulate body temperature
Perspiration is a means of certain animals, particularly primates and humans, as a means to regulate body temperature. In humans, it is carried out by the body through secreting a sweat comprised of mainly water. Other components include solutes, such as minerals, lactate, and urea, however, only in small amounts. The sweat exuded is largely water and evaporates immediately.
When the body releases sweat via the skin pores the body cools down as the water evaporates from the skin. Apart from secreting a watery fluid, perspiration also refers to the evaporation from the lungs. Thus, perspiration is a cooling mechanism of animals capable of perspiring, such as primates and humans.