lessen 1. v . to decrease.
lesson 1. n. the presentation of information, a tutorial, a teaching.
Words in the Wild: Simon’s driving lessons really seem to have lessened the frequency of his car accidents—he’s only had four of them this year.
I spotted a lessen trying to pass itself off as a lesson in a document I was editing last week. These words sound identical and on a cursory glance almost look identical, too. It’s an easy one to miss in your writing.
Still vexed? You can find a complete list of the Word Blog’s lexical vexations here.