Annual herbs, glabrous or with scattered simple hairs. Leaves variable in shape and size. Inflorescence a corymb. Sepals inclined, spreading or reflexed, inrolled; petals shortly clawed, yellow; stamens 6; ovary usually sessile. Fruit cylindric, elongate (at least 3 times as long as broad, excluding beak); valves with 3–7 veins; beak usually flattened; style short, stigma large, attenuate, depressed capitate, entire or bilobed; seeds spherical, numerous in valve region, 1 row per locule, 0 or 1 in beak.
10 species from Europe and the Mediterranean region; 2 naturalised in Australia.
Sinapis is very similar to Brassica but the fruit-valves have 3–7 strong veins and at least some sepals spreading or reflexed. Sinapis alba is well characterized by the strongly compressed, broad beak which is at least as long as the valves, but S. arvensis may be confused with a number of Brassica species. The upper stem leaves of Sinapis, however, are never stem-clasping or broadened at the base.