Permanent, that is irreversible arrest of functions of organs necessary to sustain life (regardless of the period following life birth), as a result of which all the life functions of an organism stop.

In the period from January 1, 1963 to June 30, 1994 in the Polish statistical reporting (both medical and state) death was regarded as cessation of all signs of life, regardless of the period following life birth, ascertained by persons authorized thereto, except for cases qualified as birth of infants unable to live showing signs of life (see: term "Birth"). According to principles in force at that time, the categories "infants unable to live showing signs of life" were treated as a separate group of cases not included statistically as life births, and as a result of which not qualified (in line with this definition) as infant deaths. The method of classifying live births, and in consequence infant deaths, applied in Polish statistics in years 1963 - 1993 was the main cause of lack of full comparability of this data in international scale; this related mainly to infant death ratio. The new resolution of the Minister of Health and Social Care, dated July 1, 1994, introducing new definitions of terms related to, i.a. infant deaths, restored the compliance of the discussed definitions in force in Polish statistics with the definitions recommended by the World Health Organisation (WHO). The information about births and deaths, including infant births and deaths (both absolute numbers and ratios) for the years 1963 - 1993 were calculated according to the definition currently in force.