internal cause; intrinsic motivation
Used in medical, psychological, or philosophical contexts to refer to a cause originating from within a system or person, as opposed to an external cause (外因).
病気の内因と外因を区別することが重要だ。
It is important to distinguish between internal and external causes of illness.
彼の行動の内因は、強い好奇心にある。
The intrinsic motivation behind his actions is a strong curiosity.
endogenous; intrinsic
death from natural causes
Compound of 内 (internal) and 因 (cause). The exact historical derivation is uncertain, but the term is used in modern technical contexts.