Good night and goodnight are two terms that are often used interchangeably, but there is actually a subtle difference between them.
Good night is a phrase that is typically used as a farewell at the end of a conversation or gathering. It implies that the speaker wishes the recipient of the phrase a peaceful, restful night.
Goodnight, on the other hand, is usually used as a salutation at the start of a conversation or gathering. It implies that the speaker wishes the recipient of the phrase a peaceful, restful evening.
The difference between the two phrases is subtle, but it is important to note that goodnight is used more often as a greeting, while good night is used more often as a farewell.
In addition to being used in conversation, both phrases are often used in literature, music, and other forms of entertainment. They are used as a way to indicate the end of a particular story or scene, or to create a peaceful, calming atmosphere.
When used in this way, both phrases are often written as one word, goodnight. This is because the phrase is used as an exclamation or a signal of farewell, and the two words are meant to be said together.
So, to summarize, the difference between good night and goodnight is subtle but important. Good night is used as a farewell, while goodnight is used as a greeting. In literature, music, and other forms of entertainment, both phrases are often written as one word, goodnight.