I know they all refer to unusual behaviour in a person. But in modern life while you work and you meet a native speaker of English in America and then there is a conversation what do the words really mean?
Learn English – Question about difference between “nut” and “eccentric” and “crazy” while talking to natives
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Related Solutions
What about the concise, memorable, and conveniently alliterative expression WHILE YOU WAIT, which is sometimes seen on business signs?
If someone can remember that three-word phrase (and the pictures I've added might help someone do just that), then it might be easier for them to remember how while would be the word that means "during some time interval."
Once you get one half of a confusing pair straight in your mind, the other half pretty much falls into place by default. But if you wanted something more, you could simply imagine the business owner saying:
I can fix this while you wait; you won't pay until I'm done.
Agree with your ranking of formality. I would say that "immediately," "right away," and "at once" are very similar in meaning and implied urgency. "Promptly" seems less urgent to me.
On the other hand, thesaurus.com equates "promptly" with "immediately."
Best Answer
From American Heritage Dictionary -
This would indicate that the terms nutty, crazy and eccentric may be interchangeable in some contexts.
Now my opinion (sorry, not a native though!).
When you call someone 'crazy', it adds a bit of danger there (Don't go near him, he's crazy, he can beat up you); nut is more kind of a fool, funny looking OR (at times innocent? -I remember Mary Jane calling you are such a nut to Peter Parker); eccentric is a person with odd or unusual personality.