The survival function is a function that gives the probability that a patient, device, or other object of interest will survive past a certain time.[1] The survival function is also known as the survivor function[2] or reliability function.[3] The term reliability function is common in engineering while the term survival function is used in a broader range of applications, including human mortality. The survival function is the complementary cumulative distribution function of the lifetime. Sometimes complementary cumulative distribution functions are called survival functions in general.