What is the name of the reaction where an acid and base neutralize each other?

The reaction in which an acid and a base neutralize each other is called neutralization.

In the familiar aqueous case, an acid reacts with a base to form salt and water. For example, hydrochloric acid and sodium hydroxide react as HCl + NaOH → NaCl + H₂O. At the ionic level, the key process is the reaction of hydrogen ions with hydroxide ions to form water. The spectator ions remain in solution and form the salt.

Neutralization is central to acid–base titrations. The point at which the reacting quantities are chemically equivalent is called the equivalence point. With a strong acid and strong base, the solution is close to pH 7 at room temperature, but that is not a universal rule. A weak acid or weak base can produce an equivalence solution that is acidic or alkaline.

The term does not mean every particle has vanished or that every resulting solution has exactly neutral pH. It means the acid–base reaction has consumed the relevant acidic or basic equivalents. Neutralization also occurs outside simple beakers, including when agricultural lime reduces soil acidity or limestone reacts with acid.