Touch the person lightly on the arm or shoulder when you're talking.

当你们在谈论时，轻轻地触碰他人的手臂或者肩膀。

youdao

I touch him lightly on the arm.

我轻轻地碰了他胳膊。

youdao

I touch him lightly on the arm.

我轻轻地碰了他胳膊。

youdao