At the beginning (of something) 意為「在 (某事物) 開始時；開頭部分；開端」，其後經常接介系詞 of。In the beginning 意為「起初，當初；開始時，一開始 (用來與時間上的「後來」相對)」，與 at first 和 at the start 同義 (beginning 和 start 的前面皆可用 very 來修飾)，其後不接介系詞 of。例如：
- At the beginning of every lesson, the teacher gave us a quiz. (每堂課開始時，老師都會給我們小考) (正)
In the beginning of every lesson, the teacher gave us a quiz. (誤) - I’ll go abroad for two weeks at the very beginning of May. (五月初我會出國兩個禮拜) (正)
I’ll go abroad for two weeks in the very beginning of May. (誤) - Children are still at the beginning of their lives. (兒童仍處於他們生命的初期) (正)
Children are still in the beginning of their lives. (誤) - In the beginning the main energy source was wood. (最初主要能源是木材) (正)
At the beginning the main energy source was wood. (誤) - In the beginning I didn’t know what had happened. (起先我不知道發生了什麼事) (正)
At the beginning I didn’t know what had happened. (誤) - If at first you don’t succeed, try, try again. (一次不成功，那就再接再厲) (正)
- He was a bit shy at the (very) start. (他開始時有點害羞) (正)
At the end (of something) 意為「最後部分，末尾」，其後經常接介系詞 of。In the end 意為「最後，終於」，與 at last 和 at length 同義，其後不接介系詞 of。例如：
- My room was situated at the end of the corridor. (我的房間位在走廊的盡頭) (正)
My room was situated in the end of the corridor. (誤) - At the end of the movie, everyone was crying. (電影結束時，每個人都哭了) (正)
In the end of the movie, everyone was crying. (誤) - I’m going on holiday at the end of this month. (這個月底我要去度假) (正)
I’m going on holiday in the end of this month. (誤) - In the end, we decided to move to Taipei. (最後我們決定搬到台北) (正)
At the end, we decided to move to Taipei. (誤) - Everything will turn out all right in the end. (最後一切都會好轉的) (正)
Everything will turn out all right at the end. (誤) - At last I succeeded. (最後我成功了) (正)
- At length they reached Bangkok. (他們終於抵達曼谷了) (正)