# Certainty, reliability

Reliability theory is the theory studying the probability of correct functioning of a manufactured system. The reliability of such a system is its probability of functioning correctly (and, hence, the reliability is $\leq1$, in general). The reliability function is the same probability as a function of time and/or other parameters involved in the system. There is, e.g., the reliability function of a communication channel, cf. Erroneous decoding, probability of.