If you wonder about something, you think about it, either because it interests you and you want to know more about it, or because you are worried or suspicious about it.

If you say that it is a wonder that something happened, you mean that it is very surprising and unexpected.

Wonder is a feeling of great surprise and pleasure that you have, for example when you see something that is very beautiful, or when something happens that you thought was impossible.

A wonder is something that causes people to feel great surprise or admiration.

If you refer, for example, to a young man as a wonder boy, or to a new product as a wonder drug, you mean that they are believed by many people to be very good or very effective.

If you say that someone or something is a nine-day wonder or a one-day wonder, you disapprove of the fact that they are attracting so much interest and attention, because you think that their popularity will only last for a very short time.

You can say 'I wonder' if you want to be very polite when you are asking someone to do something, or when you are asking them for their opinion or for information.

If you say 'no wonder', 'little wonder', or 'small wonder', you mean that something is not surprising.

You can say 'No wonder' when you find out the reason for something that has been puzzling you for some time.

If you say that a person or thing works wonders or does wonders, you mean that they have a very good effect on something.