Oxidation is a reaction in which a species loses electrons.

Here's why:

* Oxidation: The loss of electrons by an atom or ion. This results in an increase in the oxidation state of the species.

* Reduction: The gain of electrons by an atom or ion. This results in a decrease in the oxidation state of the species.

Remember: Oxidation and reduction always occur together in a chemical reaction, known as a redox reaction. One species is oxidized while another is reduced.

Example:

In the reaction of iron with oxygen to form rust (iron oxide), iron is oxidized and oxygen is reduced.

* Iron (Fe) loses electrons: Fe → Fe²⁺ + 2e⁻ (Oxidation)

* Oxygen (O₂) gains electrons: O₂ + 4e⁻ → 2O²⁻ (Reduction)