l

In a sentence

• 她拿起了书，准备开始阅读。

  She picked up the book and was ready to start reading.

  Here, '了' is used to indicate a completed action or a change in state.

• 天气变冷了，我们应该多穿些衣服。

  The weather has become cold; we should wear more clothes.

  In this example, '了' demonstrates a change in state or condition.

• 我吃了午餐，现在感觉很好。

  I ate lunch, and now I feel good.

  Here, '了' is used to signify a completed activity or action.