excuse v.原諒；寬恕
May I be excused?
我能被允許(做某事)嗎？
You're excused.
你被允許了。(可以的)
May I be excused from attending your lecture today?
我今天能不去參加您的講座嗎？

excuse n.借口；理由
There's no excuse for being late three days in a row.
連續(xù)遲到三天！沒有借口！說不過去！

Excuse me. 不好意思抱歉／不好意思打擾一下。
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".
當你不小心做了一個什么事情你覺得有點抱歉… 比如在公交車上撞了一下別人... 或者想要打斷某人的說話或者想法。在這種情況下你可以說“excuse me”。

Excuse you. 你冒犯到我了！
It is something people say when they are very annoyed.
當覺得惱怒的時候，可以講這句話。

Excuse my French. 并不是說“抱歉我的法語不好”。
It's said when you are pretending to be sorry for using a word that may be considered offensive.
不小心說話粗魯了，說臟話了，在說錯話的時候，可以用這句來道歉。但是常常是有點賤賤的，假裝抱歉。