The primary ingredient in traditional vegetable soup is typically a variety of vegetables. Commonly used vegetables may include carrots, potatoes, celery, onions, and tomatoes, which provide flavor, nutrition, and color to the soup. The vegetables are usually sautéed or boiled in water or broth to create a savory base. Additionally, herbs and spices may be added to enhance the flavor. Vegetable soup is a versatile dish, allowing for the inclusion of seasonal produce and personal preferences, making it a healthy and comforting meal option for many people.