プログレッシブ和英中辞典(第4版)の解説
－ので
((接続助詞)) because of; owing to; on account of; as; since; because; so... that（▼直接的な原因を表すのはbecause．sinceとasは付随的な原因を表す）
天気が悪かったので外出できなかった
I could not go out 「because of [on account of] the bad weather.／Because the weather was bad, I could not go out.
彼は非常に長い距離を歩いたのでそれ以上歩けなかった
He had walked so far that he couldn't walk any further.
村人が親切にしてくれたので旅人は間もなく回復した
「Owing to [Thanks to] the kindness of the villagers, the traveler soon recovered his health.
休暇が終わったので学生たちは学校へ戻って行った
The vacation having ended, the students went back to their schools.