Brassica rapa L. (syn. Brassica campestris L.), commonly known as turnip, turnip rape, fast plants, field mustard, or turnip mustard is a plant widely cultivated as a leaf vegetable (see mizuna and napa cabbage), a root vegetable (see turnip), and an oilseed (but not normally rapeseed oil, from a different Brassica species).
In the 18th century the turnip and the oilseed-producing variants were seen as being different species by Carolus Linnaeus who named them B. rapa and B. campestris. 20th-century taxonomists found that the plants were cross fertile and thus belonged to the same species. Since the turnip had been named first by Linnaeus, the name Brassica rapa was adopted.
The oilseeds known as canola are sometimes particular varieties of Brassica rapa (termed Polish Canola) but mostly the related species Brassica napus and Brassica juncea.