Acidity, often described as sourness, is a basic taste sensation that occurs when certain substances release hydrogen ions in solution. Common examples of acidic substances include lemons, vinegar, and yogurt. These foods typically have a pH level below 7, which indicates their acidic nature. The perception of acidity is important in various fields, including cooking and food preservation. It can enhance flavors, balance sweetness, and act as a preservative. Understanding acidity helps in creating well-rounded dishes and maintaining food safety, as many bacteria cannot thrive in acidic environments.