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something to rely on; aid; clue; way; means
someone to rely on; relative
reminder; memento
「因」 has other readings with different meanings.
古い写真が因となって思い出が蘇った。
An old photo served as a clue and brought back memories.
彼の言葉が問題を解く因になった。
His words became the key to solving the problem.
何か因になるものがないか探した。
I searched for something that could serve as a clue.