Broccoli is an edible green plant in the cabbage family (family Brassicaceae, genus Brassica) whose large flowering head and stalk is eaten as a vegetable. The word broccoli comes from the Italian plural of wikt:broccolo#Italian, which means "the flowering crest of a [[cabbage", and is the diminutive form of brocco, meaning "small nail" or "sprout". Broccoli is classified in the Italica cultivar group of the species Brassica oleracea. Broccoli has large flower heads, usually dark green in color, arranged in a tree-like structure branching out from a thick stalk which is usually light green. The mass of flower heads is surrounded by leaves. Broccoli resembles cauliflower, which is a different cultivar group of the same Brassica species. In 2017, China and India combined produced 73% of the world's broccoli and cauliflower crops. Broccoli has its origins in primitive cultivars grown in the Roman Empire. It is eaten raw or cooked. Broccoli is a particularly rich source of vitamin C and vitamin K. Contents of its characteristic sulfur-containing glucosinolate compounds, isothiocyanates and sulforaphane, are diminished by boiling, but are better preserved by steaming, microwaving or stir-frying. Rapini, sometimes called "broccoli raab" among other names, forms similar but smaller heads, and is actually a type of turnip (Brassica rapa).