水筒是一种可以装水的瓶子，人们出门的时候常常带着它。

A 水筒 is a bottle that can hold water, often carried by people when they go out.

运动或者去学校的时候，很多人都会用水筒喝水。

Many people use a 水筒 to drink water when exercising or going to school.