pen是可数名词。复数直接加s即可。如10 pens.

pen：n.笔;钢笔;圈;围栏;畜栏.

相关介绍

None of these pens works/ work.

这些钢笔没有一支能用。

She reached inside her bag for a pen.

她把手伸到包里掏钢笔。

He stopped writing and looked at me, pen poised.

他手握钢笔，停下来望着我。