half centre

例句：

1. 1.He was in the middle of the conversation when his phone rang.
   他正聊着天，电话响了。
2. 2.The center of the city is bustling with activity.
   市中心非常繁忙。
3. 3. She decided to take half a day off work to enjoy her weekend.
   她决定请半天假来享受周末。