因由 (yīnyóu): reason; cause

Meanings

Zhè jiàn shì de yīnyóu shuō lái huà cháng.

The reasons behind this matter are a long story.

Tā bù kěn shuōmíng cízhí de yīnyóu.

He won't explain the reasons for resigning.

register

Slightly literary; in everyday speech, 原因 (yuányīn) is more common. 因由 carries a hint of 'the whole backstory', not just a single cause.

culture

In Buddhist contexts overlaps with 因缘 (yīnyuán), the karmic causes and conditions that bind people across lifetimes.

因 yīn

由 yóu