（～が～する）前に, （～が～）しないうちに
反対語after （（～が～した）後で）
I must go home before it gets dark.
I must go home before it gets dark.
暗くなる前に[暗くならないうちに]私は家に帰らなければならない.
⦣ 文＋before＋文.
Do it right now, before you forget.
Do it right now, before you forget.
すぐそれをしなさい, 忘れないうちに.
Bob went out before I knew it.
Bob went out before I knew it.
（私がそれを知る前に）いつのまにかボブは外へ出て行った.
It was a long time before he knew it.
It was a long time before he knew it.
（彼がそれを知る前は長かった）長い間たってから彼はそれを知った.
It was not long before he knew it.
It was not long before he knew it.
（彼がそれを知る前は長くなかった）まもなく彼はそれを知った.
