informant

The police relied on a confidential informant to locate the hidden warehouse of stolen goods.

(Chinese) 警方依靠一名秘密线人找到了存放被盗物品的隐蔽仓库。

In linguistic field research, the native speaker acting as an informant is crucial for data collection.

(Chinese) 在语言学实地调查中，作为语料提供人的母语使用者对数据采集至关重要。