英語成語、短語、慣用語很多。有時，它們的構造看起來不合邏輯，甚至不合常理，但又不能隨意更改。例如，我們用雙腳步行，應該是on feet，但偏偏是on foot纔對。一般上說，成語、短語或慣用語中的字眼不可用別的字取代，詞序也不可調換，因爲一字之差，詞序一換，原意可能走樣，甚至毫無意思。
在下列各組句子中，（a）錯、（b）對：
①a. What is the reason of all this shunning away from blue-collar work?
b. What is the reason of all this shying away from blue-collar work?
②a. I am working on the behalf of my company.
b. I am working on behalf of my company.
③a. We need a capable person to help us in time of difficulties.
b. We need a capable person to help us in times of difficultes.
④a. In term of economic development, our country has done a good job.
b. In terms of economic development, our country has done a good job.
⑤a. Few would like to make friend with hypocrites.
b. Few would like to make friends with hypocrites.
⑥a. Lets discuss this matter in details.
b. Lets discuss this matter in detail.
⑦a. That rich woman is covered with jewellery from top to toes.
