The onion (Allium cepa) is a widely cultivated vegetable known for its pungent flavor and distinctive aroma. Belonging to the genus Allium, which includes garlic, shallots, leeks, and chives, onions are used in various culinary dishes worldwide, prized for adding depth of flavor to savory dishes.

Onions have a round, bulbous shape with several layers of papery skin surrounding the edible flesh. They range in size from small pearl onions to large, softball-sized bulbs. The color varies by variety, with common colors including white, yellow, and red/purple. Raw onions have a strong, pungent flavor ranging from mildly sweet to intensely sharp, depending on the variety. When cooked, onions develop a sweeter, milder flavor and a rich, savory aroma due to caramelization.

Several onion varieties, including yellow, white, red/purple, and sweet onions, each have a unique flavor profile and culinary uses. Onions are low in calories but rich in minerals, vitamins, and antioxidants, containing vitamin C, vitamin B6, folate, potassium, and various antioxidants such as quercetin and sulfur compounds.

A versatile ingredient, onions can be sliced, chopped, diced, or caramelized and added to soups, stews, sauces, stir-fries, salads, sandwiches, and more. Raw onions are commonly used in salads, salsas, and relishes for their crisp texture and sharp flavor, while cooked onions add depth and complexity to various dishes.