in the middle of ,“在…的中間/中點(diǎn)/中部/中央”等,是強(qiáng)調(diào)的“點(diǎn)”的概念；
英文解釋：point or position, which is at an equal distance from two or more points, etc;
point between the beginning and the end.
而in the middle part of 強(qiáng)調(diào)的是部分的概念,即是一個(gè)范疇或者說范圍問題.