关于四年级上册英语第三单元常用表达法包括以下内容：
1. 问候：Hello! Hi! Good morning/afternoon/evening! How are you? What's your name?
2. 自我介绍：My name is ___. I am ___ years old. I am from ___.
3. 询问和回答年龄：How old are you? I am ___ years old.
4. 询问和回答国籍和所属地区：Where are you from? I am from ___.
5. 询问和回答日常活动：What do you do in the morning/afternoon/evening? I usually ___.
6. 询问和回答家庭成员：How many people are there in your family? There are ___ people in my family. Who is in your family? My family members are ___.
7. 询问和回答兴趣爱好：What do you like to do? I like to ___.
8. 询问和回答身体状况：How are you feeling? I am feeling ___.
9. 询问和回答喜好食物：What is your favorite food? My favorite food is ___.
10. 询问和回答学习情况：What subjects do you study? I study ___.
以上是四年级上册英语第三单元常用的表达法，希望对你有帮助！