老實說，這三個動詞一點關係也沒有，但它們有一共通點，那就是它們都是及物動詞，後面直接接受詞，不可以接介系詞再接受詞。英文中有許多這樣的動詞，這裡只是以這三個我們常見但經常用錯的動詞作代表。總之，當 approach, discuss 和 lack 做及物動詞用時，那麼 approach to + 受詞，discuss about + 受詞，lack of + 受詞的寫法都是錯的。例如：
Silently we approached the enemy’s camp. (正)
Silently we approached to the enemy’s camp. (誤)
(我們悄悄地逼近敵人的營地)
He’s approaching 70. (正)
He’s approaching to 70. (誤)
(他快70歲了)
She discussed her study plan with her mother. (正)
She discussed about her study plan with her mother. (誤)
(她和母親討論她的讀書計畫)
Mr. Wang refused to discuss the matter. (正)
Mr. Wang refused to discuss about the matter. (誤)
(王先生拒絕討論這件事)
He’s good at his job but he seems to lack confidence. (正)
He’s good at his job but he seems to lack of confidence. (誤)
(他善於工作，但似乎缺乏信心)
I don’t seem to lack anything. (正)
I don’t seem to lack of anything. (誤)
(我好像什麼都不缺)
然而，這三個動詞的名詞 approach, discussion 和 lack 則都必須先接介系詞再接受詞。例如：
I like her approach to the problem. (我喜歡她解決這問題的方法)
We had a discussion about our future plans last night. (我們昨晚討論了我們未來的計畫)
He cannot buy this watch because of his lack of money. (他因缺錢買不起這個手錶)