dilemma [di- = two 二；lemma= premise 假設=>“a choice between two premises在兩種假設之間選擇”→]n. difficult choice between two undesirable things 窘境，進退兩難 / Her dilemma was whether to marry Paul, who was poor, or Charles, who was ugly. 使她左右為難的是，嫁給窮光蛋保羅呢，還是嫁給丑八怪查爾斯。

由di-開頭的術語為數(shù)不少，這里舉3個例子說明。

dioxide [di- = two二; oxide n. 氧化物→] n. an oxide having two atoms of oxygen for each molecule 二氧化物 / Things can not burn in carbon dioxide.東西不能在二氧化碳中燃燒。

divalent [di- = two 二； valent a. 化學價的→]a. having a valence of two; bivalent 二價的 / Oxygen is a divalent element.氧是一種二價的元素。

diatomic [di- = two 二； atom n. 原子；-ic a. = having 有… →]a. having two atoms in each molecule 雙原子的 / Oxygen molecule is diatomic. 氧分子是含雙原子的。