“Grown up” is correct as an adjective and a noun. We use it most commonly to refer to people who are acting maturely or being adults. “Grown-up” is the correct adjective verb but on… See more

“Grownup” is never written as one word. You should avoid using it in this form because it does not have the same meaning that we expect. It’s best to keep “grown” an… See more

“Grown up” works as two words as both an adjective and a noun. However, it’s more common to write it as two words when it’s in the noun form because it follows more convention… See more

“Grown-up” should only be hyphenated when used as an adjective and when it modifies a noun that comes directly after it. This is fairly common in English, especially when talkin… See more