Identify a common ingredient used for thickening sauces.

Cornstarch is a common ingredient used for thickening sauces due to its unique properties. When heated with a liquid, cornstarch gelatinizes, which means it absorbs the water and swells, creating a thicker consistency. This process happens at a relatively low temperature compared to other thickening agents, allowing for quick and efficient thickening without needing to cook for long periods. Additionally, sauces thickened with cornstarch maintain a clear appearance, making it a preferred choice for certain culinary applications, such as Asian sauces and gravies.

While butter and flour can also play roles in thickening sauces, they do not work in the same way as cornstarch. Butter is often used for richness, and when combined with flour, it forms a roux which thickens over a longer cooking process. Sugar, on the other hand, is primarily used to add sweetness and does not thicken sauces in the way cornstarch does. Therefore, cornstarch is an effective and versatile thickening agent that is widely used in various culinary traditions.