An operative person or thing.
Any of a class of behaviors that produce consequences by operating (i.e., acting) upon the environment.
That operates to produce an effect.
Something or someone reliable or dependable
Suitable or fit to be relied on; worthy of dependence, reliance or trust; dependable, trustworthy
Such that either a sent packet will reach its destination, even if it requires retransmission, or the sender will be told that it didn't