Answer:
An acid is a substance that releases H⁺ in aqueous solution.
Explanation:
There are different acid-base theories, such as Arrhenius, Bronsted-Lowry, Lewis, etc.
According to the Arrhenius theory, an acid is a substance that releases H⁺ in aqueous solution.
HCl(aq) → H⁺(aq) + Cl⁻(aq)
On the other hand, according to the Arrhenius theory, a base is a substance that releases OH⁻ in aqueous solution.
NaOH(aq) → Na⁺(aq) + OH⁻(aq)