In chemistry, a base is thought of as a substance which can accept protons or any chemical compound that yields hydroxide ions (OH–) in solution. It is also commonly referred to as any substance that can react with an acid to decrease or neutralize its acidic properties, change the color of indicators (e.g. turn red litmus paper blue), feel slippery to the touch when in solution, taste bitter, react with acids to form salts, and promote certain chemical reactions (e.g. base catalysis). Example of simple bases are sodium hydroxide and ammonia. Sodium hydroxide (NaOH), also known as caustic soda or lye, dissociates in water to form hydroxide ions (OH–) and sodium ions (Na+).
Bases have many practical uses, and several of them are commonly found in the home. Household ammonia is a familiar cleaning agent. Lye is used for cleaning clogs and sink drains. Potassium hydroxide, also called caustic potash, is used to make soft soap that dissolves in water with ease. Magnesium hydroxide in water (also called milk of magnesia) is used as an antacid or laxative.