Cayenne pepper -- also known as the Guinea pepper or bird pepper or, especially in its powdered form, red pepper -- is a hot, red chili pepper used to flavor dishes and for medicinal purposes. Named for the city of Cayenne in French Guiana, it is a cultivar of Capsicum annuum related to bell peppers, jalapeños, and others. The Capsicum genus is in the nightshade family (Solanaceae).
The fruits are generally dried and ground, or pulped and baked into cakes, which are then ground and sifted to make the powdered spice known as cayenne pepper.
Cayenne is used in cooking spicy dishes, as a powder or in its whole form (such as in Sichuan cuisine) or in a thin, vinegar-based sauce. It is generally rated at 30,000 to 50,000 Scoville Units. It is also used as a herbal supplement, and was mentioned by Nicholas Culpeper in his 17th century book Complete Herbal.