1、sad 比较级是sadder 。因为sad是单音节单词，所以不需要变成more sad 或者most sad的形式。 2、adj. 难过的；悲哀的，令人悲痛的；凄惨的，阴郁的（形容颜色）。 3、[例句]Once I had a little dog who used to look at me with sad eyes when I coughed: he was the only...