WE probably know that ‘fun’ can act as a noun and means enjoyment, pleasure, or a thing that gives enjoyment or pleasure and makes one feel happy. For example: “It would be great fun if we all go camping in Cheung Chau (長洲) together.” Now look at the Baby Blues cartoon. The wife mentions ‘a fun alternative’ in her last sentence. Here, ‘fun’ seems to be an adjective.
Yes, ‘fun’ can act as an adjective and its meaning is similar to the noun form.
In other words, ‘fun’ can mean enjoyable or making people happy. Therefore, when the wife suggests to the husband: “Come up with a fun alternative!”, what she means is: “Think of another thing to do that is enjoyable and makes people happy!” Another example: “Every kid in the kindergarten likes him because he is really fun to play with.”
You also probably know that ‘fun’ has another common adjective form: ‘funny’. However, ‘funny’ does not mean enjoyable or making people happy. It has two common meanings. First, ‘funny’ can mean making people laugh because something is interesting. For example: “Such a practical joke (ie, a trick that is played on somebody to make them look stupid and to make other people laugh) is not funny at all because you may hurt somebody.”
Second, ‘funny’ can mean weird and difﬁ cult to explain or understand. For example: “The funny thing is that the thief stole all the clothes in the ﬂ at but did not take any money.”