Final answer:
Reduction in its modern scientific sense refers to the gain of electrons in a chemical reaction. It is the opposite of oxidation and can involve the loss of oxygen, gain of hydrogen, or gain of electrons.
Step-by-step explanation:
In its modern scientific sense, the term 'reduction' means the gain of one or more electrons in a chemical reaction. The substance that gains electrons is said to be reduced. Reduction is the opposite of oxidation and is often represented by the loss of oxygen, gain of hydrogen, or gain of electrons. An example of reduction is the extraction of iron from iron (III) oxide by reacting it with carbon at high temperatures.