Origin: Germanic Old English prefix
Overnight has 7 different meanings across 2 categories:
Items delivered or completed overnight.
"The courier confirmed that your package would arrive at your doorstep overnight after you selected the express shipping option."
In plain English: An overnight is the period of time that passes while you are sleeping through the night.
"I packed my bag to sleep overnight since I had no other place to stay."
Usage: Use "overnight" as a noun to refer specifically to items that are delivered or services completed within a single night, such as in the phrase "an overnight package." Avoid using it as a noun when you simply mean the duration of time between evening and morning.
To stay overnight; to spend the night.
"I'll be staying at my sister's house, so I won't be able to make it home tonight and will have to sleep over there instead of driving back immediately after work."
In plain English: To spend the night somewhere instead of going home.
"The storm overnighted in the valley, filling the air with heavy rain and wind."
Usage: Use "overnight" as a verb when describing the act of staying somewhere during the night, though it is often better expressed with "spend the night." In most everyday contexts, use this word sparingly since "sleep over" or "stay overnight" sounds more natural.
Occurring between dusk and dawn.
"The package arrived at my door just after midnight, proving that it had truly traveled overnight."
In plain English: Overnight means something that happens during the night and is finished by morning.
"The snow turned into an icy sheet overnight."
Usage: Use "overnight" as an adjective to describe something that happens or exists during the night, such as an overnight guest or overnight success. Avoid using it for events occurring strictly between dusk and dawn unless the specific timing of those hours is the primary focus.
happening in a short time or with great speed
"these solutions cannot be found overnight!"
During or throughout the night, especially during the evening or night just past.
"The package arrived overnight and was sitting on my doorstep when I woke up."
In plain English: Overnight means something that happens during the night and is finished by morning.
Usage: Use "overnight" to describe an action that happens during the night or results from something occurring while you slept. Avoid using it to mean "immediately," as that is a common mistake when describing rapid changes.
The word comes from Old English, where it originally meant "through the night." While its structure combines "over" and "night," the modern sense of spending a night somewhere likely developed independently or was influenced by German.