sad的名词形式为sadness。sad作为形容词，中文含义为“悲哀的”、“显得悲哀的”、“让人难过的”、“让人无法接受的”、“该受责备或批评的”；而sadness作为名词形式，含义有“悲伤”、“难过”、“使人悲伤的事”。
一、sad的中文含义及用法介绍
sad作为形容词，意为悲哀的;难过的;显得悲哀的;令人悲哀的;让人难过的;让人无法接受的;该受责备(或批评)的。例句有：
1、We are very sad to hear that you are leaving.
听说你要走了，我们十分难过。
2、He gave a slight, sad smile.
他露出一丝苦笑。
3、It is sad that so many of his paintings have been lost.
他的画作有很多已经失传了，真可惜。
4、It's a sad fact that many of those killed were children.
让人难以接受的是遇难者中很多是孩子。
5、You'd have to be sad to wear a shirt like that.
你穿着那样的衬衣显得老气。
6、The salad consisted of a few leaves of sad-looking lettuce.
色拉就是几片生菜的残叶。
二、sadness的中文含义及用法介绍
sadness作为名词，意为悲伤;悲痛;难过;使人悲伤(或难过)的事。例句有：
1、I felt a deep sadness.
我感到深深的悲痛。
2、All great songs are informed by a certain sadness and tension
所有很棒的歌曲都透着某种悲伤和张力。
3、There was more than a hint of sadness in his voice.
他的声音中流露出了深切的悲伤。
4、All that money brought nothing but sadness and misery and tragedy.
那笔钱带来的只有伤心、痛苦和悲剧。
5、I felt sick to my stomach with sadness for them
我为他们感到十分痛心。
6、As the evening progressed, sadness turned to rage
随着夜幕逐渐降临，悲伤变成了愤怒。
7、Her mother's eyes expressed deep sadness.
她母亲的眼中流露出深切的悲伤。
