slip of the pen：筆誤。
slip：滑倒；滑跤；滑落；差錯；疏漏；紕漏。
it was just a slip of the pen.
這只是個筆誤。
In a hurry I wrote the word dog
instead of god, It was just a slip
of the pen.
一著急我把dog寫成god了，這只是筆誤罷了。
Excuse me, but there is one slip of pen in this article I gave you.
不好意思，我給你的論文中有一處筆誤。