Acids and bases are two of the most important concepts in chemistry. They are defined in terms of their ability to donate or accept protons (H+ ions). Acids are substances that can donate protons, while bases are substances that can accept protons.

The strength of an acid or base is determined by its ability to donate or accept protons. The stronger the acid, the more easily it can donate protons. The stronger the base, the more easily it can accept protons.

The pH scale is used to measure the acidity or basicity of a solution. The pH scale ranges from 0 to 14, with 7 being neutral. A solution with a pH below 7 is acidic, while a solution with a pH above 7 is basic.