Common property resource – Resource to which anyone has free access
Public good – Nonexclusive and nonrival good: The marginal cost of provision to an additional consumer is zero and people cannot be excluded from consuming it.
Nonrival good = Good for which the marginal cost of its provision to an additional consumer is zero.
Nonexclusive good – Good that people cannot be excluded from consuming, so that it is difficult or impossible to charge for its use.
Free Rider – Consumer or producer who does not pay for a nonexclusive good in the expectation that others will.