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to explain; to preach; to advocate
to persuade; to prevail upon; to reason with; to urge (someone to do)
先生は学生に努力の大切さを説いていた。
The teacher urged students to put in the effort.
反対派を粘り強く説いて賛成させた。
Persistently persuaded the opposition into agreeing.
彼は平和の必要性を世界中で説いている。
He advocates for peace around the world.