A resource is rivalrous if one person’s consumption reduces another person’s ability to consume (e.g. foods, most private goods) and non-rivalrous if the marginal cost of providing the resource to an extra person is zero (e.g. knowledge, most software, a scenic view).
Elinor Ostrom suggests that we should think about this as a continuous metric of subtractability, rather than a binary attribute.
Q. What’s a (new) example of a rivalrous resource?
A. (e.g. a computer, a watermelon, a fishery, a river’s outflow)
Q. What’s a (new) example of a non-rivalrous resource?
A. (e.g. knowledge, a scenic view, broadcast television)