excuse v.原谅；宽恕
May I be excused?
我能被允许(做某事)吗？
You're excused.
你被允许了。(可以的)
May I be excused from attending your lecture today?
我今天能不去参加您的讲座吗？

excuse n.借口；理由
There's no excuse for being late three days in a row.
连续迟到三天！没有借口！说不过去！

Excuse me. 不好意思抱歉／不好意思打扰一下。
When you do something by accident and you feel sorry, like bumping into someone on the bus… or maybe if you need to interrupt a person's speaking or thinking. In these situations, you could say "excuse me".
当你不小心做了一个什么事情你觉得有点抱歉… 比如在公交车上撞了一下别人... 或者想要打断某人的说话或者想法。在这种情况下你可以说“excuse me”。

Excuse you. 你冒犯到我了！
It is something people say when they are very annoyed.
当觉得恼怒的时候，可以讲这句话。

Excuse my French. 并不是说“抱歉我的法语不好”。
It's said when you are pretending to be sorry for using a word that may be considered offensive.
不小心说话粗鲁了，说脏话了，在说错话的时候，可以用这句来道歉。但是常常是有点贱贱的，假装抱歉。