rate hazard rate A conditional instantaneous rate in which the numerator represents an incidence conditioned on survival to a specified time, and the denominator represents a time interval with a duration approaching zero. Harold Lehmann, Kenneth Wilkins, Joanne Dehnbostel, Brian S. Alper In the definition of Hazard Rate, the term "survival" is not literally about life and death but is used to represent existence without experiencing the event. "Hazard" as a statistical term is not specific to "bad" or "dangerous" events. A hazard rate is expressed as a unitless numerator per unit of time, occurring at a specified time, and conditioned on survival to that time. A hazard rate is mathematically the negative derivative of the log of the survival function. The survival function is the probability of surviving past a specified point in time, expressed as Pr{ T >= t }. A hazard rate is also mathematically defined as lim(dt -> 0) [ Pr{ ( t <= T < t + dt ) | ( T >= t ) } / dt ] SEVCO group hazard hazard function instantaneous hazard rate ready for release