<P> In economics, a good is said to be rivalrous or rival if its consumption by one consumer prevents simultaneous consumption by other consumers., or if consumption by one party reduces utility / ability to use to another . A good is considered non-rivalrous or non-rival if, for any level of production, the cost of providing it to a marginal (additional) individual is zero . A good can be placed along a continuum ranging from rivalrous to non-rivalrous . The same characteristic is sometimes referred to as subtractable or non-subtractable . </P> <P> Most tangible goods, both durable and nondurable, are rival goods . A hammer is a durable rival good . One person's use of the hammer presents a significant barrier to others who desire to use that hammer at the same time . However, the first user does not "use up" the hammer, meaning that some rival goods can still be shared through time . An apple is a nondurable rival good: once an apple is eaten, it is "used up" and can no longer be eaten by others . Non-tangible goods can also be rivalrous . Examples include the ownership of radio spectra and domain names . In more general terms, almost all private goods are rivalrous . </P>

When is a good or service considered to be rival in nature