also: げんゆう
A somewhat formal or literary word for the underlying reason or cause of something. Often used in explanations or investigations.
Investigate the cause of the accident.
The reason for his resignation is not clear.
Standard kanji spelling for this word.
Alternate reading げんゆう is rare; げんゆ is the standard reading.
Compound of 原 (origin, source) and 由 (reason, cause). The exact historical derivation is uncertain, but the combination naturally conveys 'original reason'.