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
My elderly grandfather died of natural causes.
The police determined it was a natural death.
自然死 is death from illness or old age, the direct opposite of 事故死, which is death caused by an accident.
Compound of 自然 (しぜん, 'natural') and 死 (し, 'death').