Overnight vs. Over Night: Which Is Correct?

You have a big test coming up, so you spend long evening hours guzzling power drinks and preparing. You later find yourself continuing well into the morning hours. Would you then say that you are studying overnight or over night?

Overnight vs. Over Night

Let’s start by clearing up any confusion: overnight is the correct spelling so long as you mean to describe something that took place “all through the night.” In most cases, over night (two words) would be incorrect and possibly considered a typo.

Overnight is an adjective or adverb for depicting something that happens throughout an evening and into the next day. Here are a few sentences where it is being used correctly:

I took an overnight flight from California to Japan. (adjective)

I had to book an overnight stay when my business trip was extended. (adjective)

Kathy let her cousins stay overnight at her apartment after the party. (adverb)

In each of these sentences, something is clearly being described as having begun on one evening and lasting until at least the next morning.

With this in mind, the quick and simple answer is that overnight is correct and over night is not—a rule that holds with one exception.

The Only Time to Use Over Night

The term over night is used correctly in a particular context: namely, when you are using “over night” in a comparative sense. For instance, you might write the following:

I like daytime over night.

Here, we use over to indicate a preference instead of duration. That same sentence could be expressed as:

I like daytime better than [I like] night.

I like daytime more than [I like] night.

I like daytime instead of night.

You can see how the meaning of “over” has changed from its application in the one-word overnight. In this specific case, using the phrase over night to mean “better than,” “more than,” or “instead of” can be correct.

Although that use is accurate, you are unlikely to come across if often. It is more likely that you will see over night as the result of a typo or incorrect usage.

Pop Quiz

Choose the correct use in each sentence.

1. There is something magical about taking a train for an [overnight / over night] journey.

2. Election results are expected to continue arriving [overnight / over night].

3. [Overnight / Over night] delivery services have become popular in recent years.

4. There aren’t many staff available to work an [overnight / over night] shift.

5. I prefer day [overnight / over night].

 

Pop Quiz Answers

1. There is something magical about taking a train for an overnight

2. Election results are expected to continue arriving overnight.

3. Overnight delivery services have become popular in recent years.

4. There aren’t many staff available to work an overnight

5. I prefer day over night.

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