The primary ingredient found in mayonnaise is oil. Typically, the oil is combined with egg yolks and either vinegar or lemon juice to create an emulsion. The process involves slowly whisking or blending the oil into the egg yolk mixture, allowing it to emulsify and thicken to a creamy consistency. Various oils can be used, such as canola, olive, or sunflower oil, each contributing to the flavor and texture of the mayonnaise. This condiment is widely used in cooking and as a base for many dressings and sauces, highlighting its versatility in culinary applications.