“一只钢笔”的英语是 a pen。例如：

1. I have a pen.

2. Do you have a pen？

3. He has a pen.

4. This is a pen.

5. I bought a pen.

6. I have a new pen.

7. It is blue and very pretty.

8. The pen writes smoothly on paper.

9. She fumbled about in her handbag for a pen.

10. He dipped his pen in the ink.