A base, in chemistry, is a substance that can accept hydrogen ions (protons) or produce hydroxide ions (OH⁻) when dissolved in water. Bases typically have a bitter taste, feel slippery to the touch, and change the color of indicators, such as turning red litmus paper blue

. There are three main definitions of bases in chemistry:

• Arrhenius base: A substance that dissociates in water to produce hydroxide ions (OH⁻), such as sodium hydroxide (NaOH) or calcium hydroxide (Ca(OH)₂)

• Brønsted-Lowry base: A proton (H⁺) acceptor, which means it can attract and bind hydrogen ions from acids. This definition includes bases that do not necessarily produce hydroxide ions, like ammonia (NH₃)

• Lewis base: An electron-pair donor that can share an electron pair with an electron acceptor (Lewis acid)

Bases react with acids to form salts and water in neutralization reactions. They are often alkaline, with a pH greater than 7 in aqueous solutions

. Common examples include metal hydroxides, oxides, and amines

. In summary, a base is a chemical substance that neutralizes acids by accepting protons or releasing hydroxide ions, exhibiting characteristic physical and chemical properties such as slipperiness, bitterness, and indicator color changes