You're a woman. You're walking into a building and a man who you don't know opens the door for you. You weren't expecting it, and you appreciate it. You smile and say this.
What a gentleman! Thank you very much.
What a ___" communicates the idea "That's really ___" or "You're really ___." Here are some examples:
If you have to throw away food that's still good, you can say:
Here's something a woman can say when a man opens a door for her:
If a lot of people show up to your event or party:
What a great turnout!
A "gentleman" was historically an upper-class, wealthy man in European society. Today, when you call someone "a gentleman", it means that you think he is polite. Because the word comes from old historical ideas, it has the feeling of being old-fashioned. So when people use it, there's usually a small sense that it's a joke.
Unfortunately, there's no word for a really polite woman, although if you tell a woman who holds a door open for you "You're such a gentlewoman", she'll probably think it's funny.
"Thank you very much" is a quite formal way to say "thanks" to someone. Because it's so formal, people sometimes use it as a joke in situations that don't really need to be so formal.
In the example at top, the speaker doesn't need to be super-formal to a stranger who opened the door. But since he did something very polite by opening the door for her, she responds with the formal and polite phrase to thank him.
A more common response if someone opens a door for you is just:
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