Define reduction in the context of electrochemistry.

In electrochemistry, reduction specifically refers to the process where a substance gains electrons. This gain of electrons reduces the oxidation state of the substance involved. When a particle, atom, or ion gains electrons, its overall charge becomes more negative, demonstrating that it has been reduced.

Understanding the concept of reduction is essential, as it is one half of the redox (reduction-oxidation) reaction, where one species is reduced and another is oxidized (loses electrons). The terminology can be tricky since reduction does not imply a decrease in mass or size but rather a change in charge. Additionally, in the context of redox reactions, reduction often occurs at the cathode of an electrochemical cell, where electrons are supplied to the species being reduced.

Other choices might mislead the reader, as they either define oxidiation (loss of electrons) or refer to changes that aren't directly related to the precise electrochemical definition of reduction. For instance, while a decrease in oxidation state is indeed linked to reduction, the most accurate and direct definition in this context remains the gain of electrons.