Explain, using an example, what is meant by 'opportunity cost'?

Opportunity cost is defined as the next best alternative forgone. This is essentially, all the other alternatives that have to be given up when you make a choice. For example, the opportunity cost of going to university is the money you could have earned whilst working. By going to university, you have to miss out on the potential wages you could have earned if you had chosen to get a job instead.