Is it goodnight or good night?
It is good night, not goodnight in formal writing. The expression “good night” is two words (e.g., “Good night, Dad! I’m going to bed now”).
However, “goodnight” (one word) is common in informal contexts and creative writing (e.g., the song “Goodnight, Irene” or the book Goodnight Moon).
When you’re writing good night wishes, the QuillBot Grammar Checker can help you spot common errors like “goodnight.”