• 原因げんいん — cause, origin
• 要因よういん — primary factor
• 因果いんが — cause and effect
• 因習いんしゅう — custom, convention
• 病因びょういん — cause of illness
• 因縁いんねん — fate, connection

The enclosure radical 囗 surrounds 大 (person), which is interpreted as someone lying down. This shape hints at passivity — someone being affected or influenced — thus forming the idea of “cause” or “reason.”

事故じこの 原因げんいんを 調しらべています。
We are investigating the cause of the accident.

因果関係いんがかんけいを 明あきらかにする。
Clarify the causal relationship.

Commonly read as “イン” in words like 原因 (cause), 因果 (karma), and 要因 (factor). It does not have commonly used kun-yomi.