Someone or something that is faithful or reliable.
The practicing members of a religion or followers of a cause.
Consistent with reality.
Reliable; worthy of trust.
Loyal; adhering firmly to person or cause.
Injective in specific contexts, e.g. of representations in representation or functors in category theory.
Engaging in sexual relations only with one's spouse or long-term sexual partner.
Having faith.
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.