middle

middle, centre, core, midst

这组词都有“中间”“中部”的意思。它们的区别在于:
1.middle指距离两端或两边相等距离的中央或中间部分,也可指一段时间或行动始末的中间一段; midst指空间、时间、事物、人群等的中间; core指果实的果心; centre指空间的方、圆等位于中心的位置。例如:
There is a double writing table in the middle of the room.房子中间放着一张双人写字台。
He was elected from the midst of the prisoners.他是从犯人中选出的。
The core of the apple is hard.苹果核是硬的。
This building is at the centre of the city.这座大楼坐落在市中心。
2.core引申为“精髓”“核心”或“重要部分”; centre则引申为重要活动或事物的中心。例如:
We didn't get to the core of the subject.我们没触及问题的核心。
The core of our appeal is freedom of speech.我们呼吁的中心是要言论自由。
She loves to be the centre of interest.她喜欢成为引人注意的中心人物。

下面两句话的意思不同:

He arrived at Yulin at the middle of May.
他是五月中到玉林的。
He arrived at Yulin in the middle of May.
他是五月中旬到玉林的。

middle school, senior middle school, junior middle school

三者的意思并不相同。它们的区别在于：middle school的意思是“中学(包括初中和高中)”,是一种比较笼统的用法; junior middle school的意思是“初中”; senior middle schools的意思是“高中”。例如:
When he studied in middle school, he was dismissed for stealing.他在中学读书时,因偷窃而被开除。
About 80 percent of the graduates advanced to senior middle schools.约有80%的毕业生升入了高中。
My brother dropped out at the end of the second year of his junior middle school.我哥哥念完初中二年级就休学了。