What defines an acid in terms of solution chemistry?

An acid is defined as a substance that increases the concentration of hydrogen ions (H+) in a solution. This characteristic is fundamental to acid-base chemistry, as the presence of H+ ions is what gives acids their distinctive properties, such as sour taste and the ability to conduct electricity in solution.

When an acid dissolves in water, it ionizes and releases H+ ions into the solution, thereby lowering the pH and creating an acidic environment. This increase in hydrogen ion concentration is a key factor in many chemical reactions, including those in biological systems, where acids can act as proton donors. Understanding this definition helps in determining the behavior of substances in various chemical reactions and interactions in both clinical and laboratory settings.