How fun it is

When expressing how enjoyable something is, both "what fun it is" and "how fun it is" can be used interchangeably. However, there is a slight difference in how they are perceived.

"What fun it is" is often used to express surprise or delight in a situation. For example, if you unexpectedly run into an old friend while out shopping, you might say "What fun it is to see you!" This phrase emphasizes the novelty and excitement of the situation.

On the other hand, "how fun it is" is used to describe the general level of enjoyment in a situation. For example, if you are having a great time at a party, you might say "How fun it is to be here!" This phrase emphasizes the overall enjoyment of the event, rather than the surprise or novelty of it.

In summary, both "what fun it is" and "how fun it is" can be used to express enjoyment, but "what fun it is" emphasizes the surprise or novelty of a situation, while "how fun it is" emphasizes the overall level of enjoyment.