This is the 1796th most frequent Japanese word.
反省
Self-reflection or introspection.
This use of "反省" conveys learning from a past mistake to avoid repeating it in the future.
彼女は失敗を反省して、同じ間違いを繰り返さないようにした。
She reflected on her failure and ensured she would not repeat the same mistake.
In this sentence, "反省" means reflecting critically on one's behavior to understand one's mistakes.
彼は自分の行動を深く反省している。
He is deeply reflecting on his actions.
Here, "反省" is presented as an action that leads to personal growth and understanding.