Goodnight is what you say to someone when parting in the evening or before going to sleep. It's a simple wish that the other person will have a good, restful night. When you say goodnight to your parents before bed, you're both saying farewell and expressing care.

The word combines “good” and “night” into a single expression. You might say goodnight when leaving a friend's house after dark, when ending a phone call in the evening, or when tucking in a younger sibling.

People sometimes get creative with goodnight. Parents reading bedtime stories might say goodnight to everything in the room, like in the classic book Goodnight Moon. Friends might text “gn” as a quick shorthand. Some families have special goodnight rituals, like saying “sleep tight” or “sweet dreams” along with it.

Notice that goodnight is for parting, while “good evening” is for greeting someone after dark. If someone arrives at your house at 8 PM, you'd say “good evening.” When they leave, you'd say goodnight.