The onion is a bulb vegetable, named after the edible part – the bulb – a group that also includes chives, garlic and leeks. The shape and size of onions vary considerably, ranging from disc-shaped to elongated and egg-shaped. The outer layers of the onion are membranous and come in various colours (white, yellow, purple, brown). The fruit is a capsule. Yellow onions usually have a brown skin. Yellow onions have a more pronounced aroma and flavour, and it is recommended to cook them before eating.