Question: “Dear Grammer Guy, thanks for the ‘opportunity’ to read your comments on appropriate word usage. I’d like to know how ‘fun’ came to be used as an adjective. I always thought ‘fun’ was a noun.” – (Wayne Carter)
Answer: You know, I went into this thinking I wouldn’t be able to give you a real date, but I was pleasantly surprised by the results of my research.
To start off with, every dictionary you look at is going to say the primary definition of “fun” is a noun meaning amusement or enjoyment. Reading is fun. Going to the movies is fun. Heck, even grammar is fun! (I swear!)
Merriam-Webster says “fun” first appeared in English usage around 1727. Oxford has it appearing in the late 17th century and denoting a trick or hoax or “to make a fool.” Both have it acting consistently as a noun until, according to Merriam-Webster, someone decided in 1846 that it would make a great adjective too.
Nowadays – more than 160 years later, mind you – the adjective entry for “fun” still has an “informal” tag next to it in the dictionary. Oxford goes even further, tagging the verb form of “fun” as a “North American informal” usage, even though that meaning – to joke or tease – is arguably the original one. You can almost hear them putting it off as “Yankee slang” through the dictionary.
To get back on track: Yes, the primary and most-correct usage of “fun” is as a noun. Despite more than a century-and-a-half of use, its adjective form is still considered informal. Maybe at 200 it will be old enough for formal usage. Hopefully our friends across the pond will warm up to our “Yankee” usage of the word as well – after all, they finally came around to us.