Ajwain (also known as Carom, Ajowan, Bishop's Weed and Seeds Of Bishop's Weed), is an uncommon spice except in certain areas of Asia. It is the small seed-like fruit of the Bishop's Weed plant, (Carum Copticum), egg-shaped and grayish in colour. The plant has a similarity to parsley.
Ajwain tastes similar to thyme because it also contains thymol oil, but it is a bit astringent, and is stronger and less subtle than thyme. It is described as having a pungent and bitter flavour, and also as having a "musty and base" flavour.
Ajwain originated in the Middle East, possibly in Egypt. It is now primarily grown and used in India, but also in Iran, Egypt and Afghanistan. It is sometimes used as an ingredient in berebere, an Ethiopian spice mixture.
The dried fruits of the plant are used. Because they look like seeds, some call Ajwain, Ajwain seed. The flavour of this spice can be improved by roasting the small fruits in a dry pan.
It is used in India and Africa, and one of the most common uses is with lentils. Supposedly it can reduce the gassy effect of beans when the two are cooked together. One suggestion is to use it along with cumin, whenever cumin is called for.