An onion, also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus Allium.

In the food context, the term "onion" refers to a flavorful and versatile vegetable that is widely used in many culinary traditions around the world. Here are some examples of how onions are used in various dishes and cuisines:

1. French Onion Soup: This classic French dish is made by sautéing onions until caramelized, then simmering them in beef broth until tender. The soup is usually served with a slice of bread and melted cheese on top.

2. Indian Curries: Onions are a staple ingredient in many Indian curries, where they are often cooked with spices and other aromatics to create a flavorful base for the dish.

3. Italian Tomato Sauce: Many Italian tomato sauce recipes start with sautéing onions until softened and translucent, then adding garlic and tomatoes to the pot.

4. Mexican Salsa: Onions are a common ingredient in many Mexican salsas, where they are typically chopped and combined with other ingredients like tomatoes, chilies, and cilantro.

5. Middle Eastern Shawarma: Onions are often used to flavor the meat in Middle Eastern shawarma, which is typically made by marinating slices of beef or lamb with spices, vinegar, and onions.

6. American Hamburgers: Sliced raw or caramelized onions are a popular topping for hamburgers in the United States.

7. Japanese Cuisine: Onions are often used in Japanese cuisine, particularly in dishes like onion soup, onion tempura, and tonkatsu sauce.

8. Thai Cuisine: Onions are a key ingredient in many Thai dishes, such as stir-fries, curries, and noodle dishes.

9. Spanish Tortilla: Onions are one of the main ingredients in Spanish tortilla, which is a type of omelet made with potatoes, onions, and eggs.

10. British Bangers and Mash: Onions are often cooked with sausages and served on top of mashed potatoes in this classic British dish.

Overall, onions are an essential ingredient in many different types of cuisine and can be used in a wide variety of dishes to add flavor, texture, and aroma.