过去式和过去分词是英语动词变化的重要形式，常用于描述过去的动作或状态。它们在句子中的作用不同，使用时需注意区别。
| 用法 | 过去式 | 过去分词 |
| 一般过去时 | He walked to school. | - |
| 现在完成时 | He has walked to school. | He has walked to school. |
| 被动语态 | The book was written by him. | The book was written by him. |
| 完成进行时 | He has been walking. | He has been walking. |
过去式通常用于描述已完成的动作，而过去分词常与助动词一起构成完成时或被动语态。掌握它们的用法有助于更准确地表达时间关系。
