Giving examples, explain the meaning of cost in economics. 

In economics, cost means those payments which must be received by resource owners in order to ensure that they will continue to supply the resources for production.
The economic costs are based on a common principle which is called opportunity cost. It is the opportunity loss of not being able to produce some other product.
Economic cost includes explicit costs, implicit costs and normal profits. Example, wages to labourer, rent to land lord, profit to entrepreneur, interest to capital etc.
Explicit cost: Explicit costs are opportunity costs that involve direct monetary payment by producers. The explicit opportunity cost of the factors of production not already owned by a producer is the price that the producer has to pay for them.
Implicit cost: Implicit costs (also called implied, imputed or notional costs) are the opportunity costs not reflected in cash outflow but implied by the failure of the firm to allocate its existing (owned) resources, or factors of production to the best alternative use.