In professional wrestling, heat refers to both crowd reaction and real-life animosity between those involved in the professional wrestling business. In terms of crowd reaction, heat is usually either cheers for a babyface (hero) or boos for a heel (villain). The amount of heat a wrestler generates is often an accurate gauge of his popularity.

Although the term can in some contexts refer to either positive or negative crowd reactions, "heat" can otherwise be used specifically to mean a negative crowd response (booing etc.); its opposite being a "pop" or positive reaction (cheering etc.).

"Canned heat" refers to playing a recording of cheering or booing through the arena's sound system or adding it to a taped show. This serves to either amplify a crowd reaction or to mask silence from the crowd. Pre-taped crowd reactions from other events are also spliced in with the programming to make it look like the crowd is more energetic than it actually is, or if promoters want a storyline to go in a particular direction. Some examples include:

Heat is energy transferred from one system to another by thermal interaction. In contrast to work, heat is always accompanied by a transfer of entropy. Heat flow is characteristic of macroscopic objects and systems, but its origin and properties can be understood in terms of their microscopic constituents.

Heat flow from a high to a low temperature body occurs spontaneously. This flow of energy can be harnessed and converted into useful work by means of a heat engine. The second law of thermodynamics prohibits heat flow from a low to a high temperature body, but with the aid of a heat pump external work can be used to transport energy from low to the high temperature.

The SI unit of heat is the joule. Heat can be measured by calorimetry, or determined indirectly by calculations based on other quantities, relying for instance on the first law of thermodynamics.

Heat transfer can occur in a variety of ways: by conduction, radiation,convection, net mass transfer, friction or viscosity, and by chemical dissipation.

Professional wrestling (often shortened pro wrestling, or simply wrestling) is a mode of spectacle, combining athletics and theatrical performance. It takes the form of events, held by touring companies, which mimic a title match combat sport. The unique form of sport portrayed is fundamentally based on classical and "catch" wrestling, with modern additions of striking attacks, strength-based holds and throws, and acrobatic maneuvers; much of these derive from the influence of various international martial arts. An additional aspect of combat with improvised weaponry is sometimes included to varying degrees.

The matches have predetermined outcomes in order to heighten entertainment value, and all combative maneuvers are worked in order to lessen the chance of actual injury. These facts were once kept highly secretive but are now a widely accepted open secret. By and large, the true nature of the performance is not discussed by the performing company in order to sustain and promote the willing suspension of disbelief for the audience by maintaining an aura of verisimilitude.

A professional is a person who is paid to undertake a specialized set of tasks and to complete them for a fee. The traditional professions were doctors, engineers, lawyers, clergymen and commissioned military officers. Today, the term is applied to architects, accountants, educators, engineers, scientists, technology experts, social workers and many more.

The term is also used in sports to differentiate amateur players from those who are paid - hence "professional footballer" and "professional golfer". Many companies include the word professional in their store name to signify the quality of their workmanship or service.

In some cultures, the term is used as shorthand to describe a particular social stratum of well educated, mostly salaried workers, who enjoy considerable work autonomy, a comfortable salary, and are commonly engaged in creative and intellectually challenging work.

Due to the personal and confidential nature of many professional services, and thus the necessity to place a great deal of trust in them, most professionals are subject to strict codes of conduct enshrining rigorous ethical and moral obligations.

Wrestling is a form of combat sport involving grappling type techniques such as clinch fighting, throws and takedowns, joint locks, pins and other grappling holds. A wrestling bout is a physical competition, between two (occasionally more) competitors or sparring partners, who attempt to gain and maintain a superior position. There are a wide range of styles with varying rules with both traditional historic and modern styles. Wrestling techniques have been incorporated into other martial arts as well as military hand-to-hand combat systems.

The term wrestling is attested in late Old English, as wræstlunge (glossing palestram).

Wrestling is one of the oldest forms of combat with references to it as early as the Iliad, in which Homer recounts the Trojan War in the 13th or 12th century BC. The origins of wrestling can be traced back 15,000 years through cave drawings in France. Babylonian and Egyptian relief's show wrestlers using most of the holds known to the present-day sport. In ancient Greece, wrestling occupied a prominent place in legend and literature; wrestling competition, brutal in many aspects, was the number one sport of the Olympic Games. The ancient Romans borrowed heavily from Greek wrestling, but eliminated much of its brutality.