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character (of a person); personality; disposition; nature
characteristics; nature (of a thing, event, etc.)
彼女は明るい性格の持ち主だ。
She has a cheerful personality.
その事件の性格は単純な強盗ではなかった。
The nature of that incident was not that of a simple robbery.
性格が合わない人とも上手く付き合いたい。
There are people whose personalities don't match.