noun
natural death; dying of natural causes
Refers to death from internal factors like illness or aging, as opposed to unnatural causes such as accidents, suicide, or homicide. Often contrasted with 異状死 (unnatural death).
See also: 異状死
高齢の祖父は自然死だった。
My elderly grandfather died of natural causes.
警察は自然死と判断した。
The police determined it was a natural death.
病死 specifically means 'death from illness', a common type of 自然死, but 自然死 also includes death from old age without a specific disease.
Compound of 自然 (しぜん, 'natural') and 死 (し, 'death').