A vital statistics summary rate based on the number of infant occurring during the same period of time, usually a calendar year, i.e., the number of deaths under one year of age occurring in a given geographical area during a given year, per 1,000 live births occurring among the population of the given geographical area during the same year.

annual number of deaths of infants under age 1 per 1,000 live births.  It is used as an indicator of the probability of dying between birth and exactly one year of age.