Turnips are a type of which vegetable?

Turnips are a root vegetable commonly associated with potatoes or beets, but their closest relatives are radishes and arugula — all members of the mustard family in the genus Brassica. Both the bulbous white and purple taproot and the leafy greens are edible. The turnips are thought to have originated in eastern Asia, but it was widely cultivated around the Roman Empire and is now grown and eaten in temperate zones around the world.

Source: The Spruce Eats