Once 的用法

Once 可當副詞、連接詞和名詞用。

Once 當副詞時意為「一次,一回」,如 We’ve met only once. (我們只見過一次面)。在這項用法中,我們經常使用 once a + 單數時間詞 (once a week/month/year etc. - 一星期/一個月/一年等一次) 及 once every + 複數時間詞 (once every two days/three years etc. - 每兩天/三年等一次) 來表示事情發生的頻率。例如:

  • We go for dinner together once a week. (我們一個禮拜會共進晚餐一次) (正)
  • We go for dinner together once the week. (誤)
  • Tom visits his parents only once every two or three months. (湯姆每兩三個月才探望他父母親一次)

Once 當副詞時還意為「從前,曾經」。在這項用法中,once 通常位在句子的中間,亦即位在主詞和主動詞之間 (即普通動詞之前),或位在語氣助動詞或第一個助動詞之後,或位在當主動詞的 BE 動詞之後。例如:

  • John once knew Mary, but they are no longer friends. (約翰以前認識瑪麗,但他們已經不是朋友了)
  • It was hard to believe that she had once been beautiful. (很難相信她以前很漂亮)
  • Egypt was once a great nation. (埃及曾經是個偉大的國家)

由當副詞用的 once 所構成的片語不在少數,其中之一就是大家所熟悉的 once upon a time。這片語意為「從前,很久以前 (童話故事的開頭)」,如 Once upon a time there was a little girl called Little Red Riding Hood … (很久很久以前,有個小女孩叫做小紅帽…),但它現在也不時用於口語中,意為「以前,過去」(long ago),如 We used to go to nightclubs once upon a time. (我們以前常上夜店)。

Once 當連接詞時意為「一旦,一 … 就 …」(as soon as)。例如:

  • Once I’ve picked Cindy up at the airport, I’ll call you. (一旦我在機場接到辛蒂,我就會打電話給你)
  • Once you get into a bad habit, you’ll find it hard to get out of it. (一旦染上惡習,就很難改掉了)

與 when, while, before, after, by the time, as soon as, if 和 unless 等所引導的時間副詞子句一樣,once 所引導的時間子句亦不可使用表示未來的 will 或 be going to。例如:

  • Once I pass all these exams, I’ll be fully qualified. (一旦我通過所有這些考試,我就完全合格了) (正)
  • Once I will pass all these exams, I’ll be fully qualified. (誤)

Once 當名詞時意為「一次,一回」,主要用於 at once (立即,馬上;同時)、all at once (突然,忽然)、(just) for once (僅此一次,就這一回,難得一次)、(just) this once (就這一次,就此一次)、(just) that once (就那一次) 及 (just) the once (就這一次;就那一次) 等片語中,或者說主要用來構成這些片語。例如:

  • Come at once! (馬上過來!)
  • They met at my birthday party and became good friends at once. (他們在我的生日派對上相識並很快成了好朋友)
  • Don’t all talk at once! (不要同時都說話!)
  • He can do two things at once. (他可以同時做兩件事)
  • She left all at once. (她突然離開了)
  • For once Jack was telling the truth. (傑克就這一回說了實話)
  • You can pay the bill just for once. (你難得一次可以付帳)
  • He only came the once. (他只來過一次)
  • Do it just the once. (就做這一次吧)
  • Sam did it just this once, but once is enough. (山姆只做了這一次,但一次就夠了)
  • We met just the/that once, but I still remember her very clearly. (我們就見了那一次,但我仍很清楚地記得她)