noun
external cause; external origin; exogenous cause
Used in medical, scientific, or analytical contexts to refer to a cause or factor originating from outside a system, organism, or situation. Often contrasted with 内因 (internal cause).
この病気の外因はまだ特定されていない。
The external cause of this disease has not yet been identified.
外因と内因の両方を考慮する必要がある。
It is necessary to consider both external and internal causes.