Ceratonia siliqua, known as the carob tree , St John's bread, locust bean, locust-tree, or carob bush is a flowering evergreen tree or shrub in the pea family, Fabaceae. It is widely cultivated for its edible pods, and as an ornamental tree in gardens. The ripe, dried, and sometimes toasted pod is often ground into carob powder, which is used to replace cocoa powder. Carob bars, an alternative to chocolate bars, as well as carob treats, are often available in health food stores. Carob pods are naturally sweet, not bitter, and contain no theobromine or caffeine. The carob tree is native to the Mediterranean region, including Southern Europe, Northern Africa, the larger Mediterranean islands, the Levant and Middle-East of Western Asia into Iran; and the Canary Islands and Macaronesia. The carat, a unit of mass for gemstones, and a measurement of purity for gold, takes its name from the Greek word for a carob seed, keration, via the Arabic word, qīrāṭ.