Lucy is the 主持人 of this evening.

Tom is the 指挥 of this activity.

我水平不行，还没毕业，为什么不去查字典呢。

Lucy was the host of the evening party.

Tom was the director of the activity.

Lucy acted as the host of the evening.

Tom is the commander of the event.

Lucy acts as the host of the party,and Tom is the director of this program.