Trachyspermum ammi, commonly known as ajwain, ajowan, carom seeds, or bishop’s weed, is an annual herb in the Apiaceae family. The genus name Trachyspermum derives from Greek trachys (“rough”) and sperma (“seed”), referring to the seed’s surface. The specific epithet ammi is derived from the ancient Greek ammi, a name for plants of the Apiaceae family. Native to the eastern Mediterranean and West Asia, early domestication is traced to the Levant, Persia, and northern India. The plant produces small, ridged seeds with a strong thyme-like flavor due to their high thymol content.

Historically, ajwain was valued in the ancient Middle East, Egypt, and India as both a spice and a medicine. Ancient texts in Ayurveda and Unani medicine describe its use for digestive disorders, respiratory ailments, and as an antimicrobial. In medieval trade, ajwain spread across the Islamic world into India, where it became a cornerstone of local cuisines. In modern times, ajwain remains integral to Indian, Pakistani, Iranian, and Middle Eastern cooking, where the seeds are used to flavor breads, lentil dishes, and pickles. They are also chewed raw as a digestive aid or brewed into teas for colds and indigestion. Globally, ajwain oil rich in thymol is used in pharmaceuticals, dental care products, and perfumery.