Goodnight and Good night are both acceptable as a way to say goodbye to someone.
The meaning of “Goodnight” or “Good night” is that the evening is finished and you are either going home or to bed.
Is Goodnight one word or two words?
Goodnight can be expressed using one word or two words. “Good night” and “Goodnight are both correct.
“Good night” was originally the only correct form (following the structure of good morning and good afternoon) but in recent times “goodnight” has also become accepted and is in fact more common than “good night”
It’s time to go to bed, say good night.
Goodnight is often used in English and is a little bit more informal. It is more often to use “goodnight” in a text message as a way to show that you want to end the conversation and go to sleep.
Ok, Goodnight! I am going to sleep.
Good night use
You can also use “Good night” as a way to say goodbye and that you are going home or to bed.
We also use “good night” when we want to describe a night as “good”.
Did you enjoy the restaurant? Oh yes, we had a good night there.
Goodnight as an adjective
“Goodnight” can also be used as an adjective when it describes a noun.
It is time for your goodnight kiss.
Goodnight as a noun
“Goodnight” can also be used as a noun but this is more common with the expression “say your goodnights” when there are a few children.
The children said their goodnights and went off to bed.