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Goodnight or Good Night: Is It Two Words or One?

Greetings and farewells are an important part of any language — they convey goodwill and acknowledge the recipient’s presence. There aren’t many variations of these in English, but one interesting case is whether “goodnight” or “good night” is the correct way to spell this particular farewell.

Use “Good night” as a farewell interjection when going to bed or parting ways at night. In contrast, we might use “goodnight” as an adjective before a noun, as in “goodnight kiss,” but it should technically have a hyphen, “good-night kiss.” Oxford dictionaries recognize “goodnight” as a compound word, while Merriam-Webster doesn’t.

We’ll take a closer look at all three of these functions and develop an understanding of why we prefer the different usages of “good night” in those cases. 

Good Night as an Interjection

Interjections are short utterances to express emotion. They very typically stand on their own, meaning we consider them as complete sentences in and of themselves.

Some other examples of interjections are “Hello!” “Bless you!” and “Oh no!” These examples show they can be anything from greetings, farewells, well-wishes, or exclamations to show how we’re feeling.

Again, there are not many English greetings or farewells one can use because they follow a very defined formula — a combination of time of day and well-wishes for the recipient.

The Greetings

We use “Good morning” during the early hours of the day, which is the most common greeting for people seeing each other for the first time that day.

We use “Good afternoon” to greet someone in the middle of the day. We still mainly use it as a greeting, though it’s less common as you would have already seen the majority of people you interact with by midday.

“Good evening” is one greeting when you meet someone at night, but we tend to view this as a rather formal greeting, so it’s possibly the least used of all the greetings. 

The acceptable spelling for all three of these greetings is with a space between the two words because “good” functions as an adjective to modify the following noun, describing the kind of morning, afternoon, or evening that the person greeting wishes for the recipient (source).

The Farewells

We can also turn these phrases into farewells, meaning phrases to end a conversation politely and wish the recipient well as you part ways. Unlike greetings, there are only two farewells based on the time of day.

“Good day” covers farewells during both the morning and afternoon. It can also be very formal and, in some ways, dismissive, so we rarely use it as a farewell anymore.

“Good night” is a farewell someone might use when the person sending their farewell does not think they will see the recipient again that day. We commonly use this when one or both parties are going to bed for the night.

The Merriam-Webster online dictionary lists “good night” as an interjection, a word or phrase grammatically independent from any words around it (source). It is understood to be a contraction of “I hope you have a good night!”

There is one farewell that covers all times of day, namely, “goodbye.” However, this follows a different set of rules, which we’ll look at closer in a later section.

With the adjective-plus-noun precedent of the five greetings and farewells, many prefer to use a space between “good” and “night” when using it as an interjection since it creates consistency.

We most commonly use it as an interjection, so we’ll most often see it as a two-word phrase.

For the remaining uses as a one-word noun or adjective, we don’t use the space, making it critical for users to understand the phrase’s function in the sentence.

This means understanding what adjective or nouns you’re using so that you can adjust your usage accordingly.

Goodnight as an Adjective

While the “good” in “good night” is an adjective describing the noun “night,” we can also use “goodnight” as an adjective to describe the nature of an action or object as in the following example (source):

Sarah refused to fall asleep until she got a goodnight kiss from her mother.

In this case, “goodnight” provides additional information and describes the nature of the kiss she requires before going to bed.

Interestingly, it only makes sense to use the phrase as one word when we use it in this way.

To separate them would only confuse the reader since we might mistake “good” as the adjective in the sentence, leaving “night kiss” as the object, which does not make much sense.

Thus, the two words that make up “goodnight” join together when we use them together as an adjective.

Should We Use a Hyphen?

This begs the question, why is “goodnight” correct when used as an adjective and not “good-night”?

We use hyphens to create compound words, joining two separate words to become one unified word. Creating this compound word can sometimes drastically change the meaning of one or both of the words or simply modify them to provide more information.

Some examples of compound words are “runner-up,” “clean-cut,” and “single-minded.”

Like “goodnight,” each component of these compound words can stand on its own, but you shouldn’t use the examples we listed without their hyphens as compounds.

Hyphenating is the general rule, and “goodnight” is simply one of the exceptions to this rule as it has gained acceptance over time. As the subject of a sentence, grammarians do not consider the word “night” to require a hyphen.

Many words start out hyphenated and eventually gain acceptance as one word.

So, while “goodnight” bears similarities to the examples of compound words provided, it would be incorrect ever to use “good-night.”

Goodnight as a Noun

We can also use “goodnight” as a noun, though only in very specific instances, making its usage rather rare.

A noun is a very versatile part of a sentence, referring to a thing, person, animal, place, quality, idea, or action. Consider the following examples:

The children said their farewells before heading upstairs for bed.

The children said their goodnights before heading up to bed.

In this example, “Goodnights” serves as a noun since it’s the object that the children share before bedtime.

This application of “goodnight” contracts into one word for clarity’s sake, much like how it was when we used it as an adjective. If we broke the words up, “nights” would be the noun, and “good” would be the adjective describing it.

One could argue that, should we have separated the words in the above example, we would still get our meaning across. While this might be true, it still puts a different spin on a sentence and may not be the case with others.

For this reason, when using “goodnight” as a noun, we write it as one word.

Should We Use a Hyphen?

Some might argue there is a stronger case to use a hyphen when using “good-night” as a noun than as an adjective. Consider this example: 

Peter was in a rush to say his good-nights as he was very tired.

Cases like “daughter-in-law” and “runner-up” are nouns that require hyphens because they link complex concepts together. However, in the case of “goodnight,” grammarians do not deem this as necessary, and using a hyphen would be incorrect.

One important hyphen caveat to mention is when a word is a proper noun, meaning the name of a song, product, company, or the like.

In this case, since it is the name of someone or something, it does not necessarily have to comply with grammatical rules, and you may exercise some creative license in how you spell or use it.

Can I Just Use Good Night for All Applications?

Sometimes, dissecting a sentence into its parts and identifying each phrase’s function can be difficult, so one might be tempted to use the most commonly used form exclusively.

One may be able to do so, given the fine margin between the two forms, but to be completely correct, it is advisable to learn how to identify the functions and let that guide which form of “good night” you use.

Interjection vs. Adjective

Identifying the required usage of “good night” helps to determine whether it needs a space or not, but learning the difference can be challenging. Here are some other examples to help you get to grips with its usage:

Are you going to bed, Frank? Good night then!

As we pointed out, we most commonly use “good night” as an interjection. It is the last thing that two people say to each other at the end of the day.

We shouldn’t capitalize “night,” as it is still a natural sentence despite being a common phrase, and we can use the other words afterward, as this example does:

I’d sleep better after I’ve said a goodnight prayer.

This example shows “goodnight” as an adjective — note that it functions as one word. The trick to identifying adjectives is that the sentence would still make sense if we removed the adjective.

In this case, the speaker points out that prayer would help them sleep better — a sentence that can stand on its own without the “goodnight” adjective. However, when we include it, we get the extra context — that the speaker would be praying just before trying to sleep.

As a Noun

I can’t believe Carol fell asleep without even a goodnight!

Here we see the writer use “goodnight” as a noun signified by the preceding article, “a.” This implies there can be plurals, as in “goodnights,” as we used in the noun section above.

By changing the function of “goodnight” to a noun, it has become an abstract object that we can assign to others, or not, as is the case in this example.

We most regularly use it to signify one’s farewell, similar to how one can say that you “said your goodbyes before leaving.” 

Good Night and Goodbye

It’s an interesting situation to be in, with two correct ways of spelling a phrase meaning nearly identical things — almost as if an error occurred so many times, many simply accepted it as correct as well. After all, the Oxford Dictionary recognizes both phrases as legitimate.

Though both find wide acceptance in their relevant usages, there are camps that argue that we should use one version for all. Still, as we’ve seen, this would be nearly impossible to decide for sure since each has its merits.

But how did we arrive in such a conundrum like this? It’s not every day that two ways of writing the same phrase can be correct, after all. Like we explored in the first section, we consider “good night” to be a farewell. 

One could even go so far as to say that it is a less permanent version of “goodbye,”  where “good night” implies the intention to see the recipient the next day, and “goodbye” conveys an air of uncertainty as to when the two parties will see each other again.

The Connection

These two phrases, “good night” and “goodbye,” are closely linked. In fact, the Cambridge Dictionary even pairs them in the same list of phrases to say goodbye with (source).

Looking at “goodbye,” one can see it is a conjunction between two words, namely, “good” and “bye.” Once again, “good” is the adjective we use to describe the wishes of the person sending the farewell.

We understand “Bye” to be connected to the root word “lullaby” and that it was a sound that mothers replicated to their children to try and get them to sleep (source). This is a rather surprising similarity to the phrase “good night.”

We only ever see “goodbye” written as one word, and, owing to the similarities between “good night” and “goodbye,” it’s understandable to want to spell “goodnight” in a similar manner,  without the space, by applying the same thinking.

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For more information on common English phrases, make sure you read our articles, on “I look forward to speaking with you” and “I look forward to talking to you.”

Image by Alex Green via Pexels

Final Thoughts

Both applications, with and without a space between the two words, are correct, as we’ve seen, in their proper context.

We’ve looked at all three ways to use “good night,” namely, as an interjection, an adjective, and a noun, and how to correctly use each application in different situations.