1. This book is really fun.
2. This book is real fun.
3. This book is great/good fun.
(I have a question. You said #1 and #2 are right, but that #2 is not right. What about 'good' fun? Is it right to use 'good fun' instead of 'great fun'? If #3 is right, why is #2 not right? In Sentence 3, 'fun' is used as a noun, for 'great' modifies 'fun'. However in Sentence 1, fun is used as an adjective, because 'really' is an adverb and modifies 'fun.' Right? What about Sentence 2. In Sentence 2, can't 'real' modify 'fun'? If 'real' can modify 'fun', fun can be used as a noun. Right? I anticipate your answering the questions. Thank you for your help.)
From the dictionary, here is the word fun:
fun
/fʌn/ Show Spelled [fuhn] Show IPA noun, verb,funned, fun·ning, adjective
–noun
1.
something that provides mirth or amusement: A picnic would be fun.
2.
enjoyment or playfulness: She's full of fun.
–verb (used without object), verb (used with object)
3.
Informal. joke; kid.
–adjective
4.
Informal. of or pertaining to fun, esp. to social fun: a fun thing to do; really a fun person.
5.
Informal. whimsical; flamboyant: The fashions this year are definitely on the fun side.
So, if you are using fun as a noun in #2, yes, that would be correct. When I first looked at it, it didn't look as good as #1. However, you ARE right in that case.
Sra
Let's break down the different sentences:
1. "This book is really fun."
In this sentence, you are correct. The word "really" is an adverb that modifies the adjective "fun." So here, "fun" is used as an adjective, describing the degree of enjoyment the book provides.
2. "This book is real fun."
In standard English grammar, the correct phrase would be "This book is really fun." However, in informal speech or certain dialects, it is not uncommon to hear people say "real fun" instead of "really fun." So while it may not be considered grammatically correct in a formal context, it is still a commonly used phrase in informal speech.
3. "This book is great/good fun."
"Great" and "good" are both adjectives that modify the noun "fun" in this sentence. So here, "fun" is indeed used as a noun, referring to the enjoyable nature of the book.
It's important to note that the usage of "fun" as an adjective or a noun differs depending on the context and the intention of the speaker/writer. So while "real fun" might not be considered grammatically correct in formal writing, it is still commonly used in certain colloquial contexts.