這兩個形容詞乍看之下宛若同義詞,但仔細探究它們在上下文中的應用,我們會發現它們的含意還是有差別的,因此有必要加以區分。Deceitful 意為 「欺詐的,不誠實的,騙人的;誤導的」,如 No one will trust a deceitful person. (沒有人會相信愛騙人的人)。Deceptive 意為「欺騙的,虛假的;誤導的,使人弄錯的」,如 Appearances are often deceptive. (知人知面不知心)。
然而,deceitful 有比較強烈的故意騙人或誤導的意圖 - 即使未成功 - 因此帶有負面的含意,如 It was deceitful of you to pretend to be an orphan. (你假裝是孤兒是騙人的行徑)。Deceptive 則強調誤導的效果或結果,但可能有,也可能沒有不誠實或故意的動機,如 She seems to have a lot of confidence, but appearances are sometimes deceptive. (她似乎很有信心,但只看外表往往靠不住/使人弄錯)。
Deceptive 的副詞 deceptively 含意亦同,如 The math question is deceptively simple, but really difficult. (這數學問題看似簡單,實則很難)。所以,deceptive advertising 雖表示該廣告會誤導民眾,但很有可能有一半是真實的,而 deceitful advertising 則大多是騙人的。因此,當 intentionally (有意地,故意地) 或 unintentionally (非故意地;非存心地) 與 deceitful 和 deceptive 搭配 (collocate) 時,我們可能見到 intentionally/unintentionally deceptive 和 intentionally deceitful,但不太可能見到 unintentionally deceitful。