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 sensation of sourness is detected by taste buds on the tongue, specifically those that respond to acidic compounds. Acidity plays a significant role in cooking and food preservation, as it can enhance flavors and inhibit the growth of harmful bacteria.