Lessen 是個動詞 (及物與不及物)，意為「(使) 減輕；(使) 降低；(使) 減少；(使) 變小」，如 The medicine will lessen the pain. (這藥會使疼痛減輕)；His fever has lessened. (他的燒退了)；The negotiations lessened the tension between Russia and Ukraine. (談判緩和了俄羅斯和烏克蘭的緊張局勢)。這個字的時態變化為 lessen, lessened, lessened, lessening, lessens。
Lesson 是個名詞，意為「課，一節課/一堂課，(教科書中的) 一課，課程；教訓」，如 These students study English, Spanish and other language lessons. (這些學生學英文、西班牙文及其他語言課程)；Lesson Five is very boring. (第五課枯燥乏味)；That guy needs to be taught a lesson. (那個傢伙得被教訓一頓)；Many people have not learned their lesson and continue to drive under the influence. (許多人沒有記取/得到教訓，繼續酒後開車)。