1. （尤为表示礼貌或尊敬的指称）女士；女子
    You can use lady when you are referring to a woman, especially when you are showing politeness or respect.

    e.g. She's a very sweet old lady...
           她是一位很和蔼的老太太。
    e.g. Shall we rejoin the ladies?
           咱们和女士们会合吧？

2. 女士们；小姐们
    You can say 'ladies' when you are addressing a group of women in a formal and respectful way.

    e.g. Your table is ready, ladies, if you'd care to come through...
           你们的桌位已经准备好了，女士们，请跟我来。
    e.g. Good afternoon, ladies and gentlemen.
           下午好，女士们，先生们。

3. （尤指旧时上层阶级的）贵妇，夫人，小姐
    A lady is a woman from the upper classes, especially in former times.

    e.g. ...the Empress and ladies of the Imperial Palace...
           皇后与皇宫里的贵妇们
    e.g. Our governess was told to make sure we knew how to talk like English ladies.
           要求家庭女教师教会我们英国贵妇般的谈吐。

4. （在英国用作对女贵族或爵士妻子的称谓）夫人，小姐
    In Britain, Lady is a title used in front of the names of some female members of the nobility, or the wives of knights.

    e.g. Cockburn's arrival coincided with that of Sir Iain and Lady Noble...
           科伯恩到时正好伊恩爵士和诺布尔夫人也来了。
    e.g. My dear Lady Mary, how very good to see you.
           亲爱的玛丽夫人，见到您真是太高兴了。

5. 淑女；端庄的女士
    If you say that a woman is a lady, you mean that she behaves in a polite, dignified, and graceful way.

    e.g. His wife was great as well, beautiful-looking and a real lady...
           他妻子也很招人喜欢，样子俏丽，是位真正的淑女。
    e.g. A lady always sits quietly with her hands in her lap.
           淑女端坐时总是双手放在膝上，不发一言。

6. 公共女厕；女洗手间
    People sometimes refer to a public toilet for women as the ladies .

    e.g. At Temple station, Charlotte rushed into the Ladies.
           一到坦普尔站，夏洛特立即冲进了女厕所。

7. （尤用于商店里或街上男子对不相识女子的称谓）女士，小姐
    'Lady' is sometimes used by men as a form of address when they are talking to a woman that they do not know, especially in shops and in the street.

lady的解释

    e.g. What seems to be the trouble, lady?...
           您遇到什么麻烦了吗，小姐？
    e.g. As she left the litter-strewn lot, an angry voice called out to her. 'Hey, lady!'
           她正要离开满地垃圾的停车场，一个愤怒的声音朝她大嚷：“喂，小姐！”

8. see also: First Lady;Our Lady