The Scoville scale is a measurement of pungency, the "spicy heat" of all chili peppers. The number of Scoville heat units (SHU) indicates the amount of capsaicin present. Capsaicin is a chemical compound that stimulates chemoreceptor nerve endings in the skin, especially the mucous membranes; pure capsaicin has a Scoville rating of 16,000,000 SHU.
The scale is named after its creator, American pharmacist Wilbur Scoville. His method, devised in 1912, is known as the Scoville Organoleptic Test. The modern commonplace method for quantitative analysis uses high-performance liquid chromatography, making it possible to directly measure capsaicinoid content.