Fast、quick 還是 quickly 呢？

Fast 和 quick 均意為「快的；迅速的」。Fast 可用作形容詞和副詞，而 quick 僅當形容詞用，其副詞為 quickly (立刻，馬上；迅速地)。雖然 quick 有時亦被用作副詞，但這並非標準英語。例如：

The police car was going so fast; it must have been chasing someone. (警車開得很快，一定是在追人) － fast 當形容詞用。
Allen walks very fast. (艾倫走路很快) (正) － fast 當副詞用。
Allen walks very fastly. (誤) －英文沒有 fastly 這個字。
He’s a quick learner/study. (他學東西很快) － quick 當形容詞用。
Mary replied very quickly. (瑪麗馬上就回覆了) － quickly 是 quick 的正規副詞。

Fast 是指速度非常快或高速的快，如火車行駛的速度、人類跑步的速度或動物奔跑的速度等等。例如：

John’s a remarkably fast runner/swimmer. (約翰是個速度非常快的跑者/游泳者) (正)
John’s a remarkably quick runner/swimmer. (誤)
I love fast cars. (我喜歡速度快的汽車) (正)
I love quick cars. (誤)

Quick 是指時間短或比預期時間來得短的快。例如：

The manager had a quick coffee and left the office. (經理匆忙喝完咖啡就離開了辦公室) (正)
The manager had a fast coffee and left the office. (誤)
Five explosions were heard in quick succession. (短時間內接連聽到五次爆炸聲) (正)
Five explosions were heard in fast succession. (誤)
Could you give me a quick answer? (你能立即給我答案嗎？) (正)
Could you give me a fast answer? (誤)
I have only time for a quick word. (我只有可以簡短跟你說幾句話的時間) (正)
I have only time for a fast word. (誤)

有時 fast 和 quick 可修飾同一個名詞，意思相同，即兩者為同義詞；但有時兩者意思不同。例如：

These companies just want to make a fast buck.
= These companies just want to make a quick buck. (這些公司只想快撈一筆)
It’s quite a fast journey. (這是一次很快就結束的旅程)
It’s quite a quick journey. (這次旅程很短)
He’s a fast worker. (他是個能快速與異性交往的人)
He’s a quick worker. (他是個做事很快的人)

必須注意的是，漢堡等速食雖以烹飪或準備時間短且可立即供應為主要特色，但其英文是 fast food，不是 quick food。例如：