Should You Capitalize the Word "Earth"?

G. Wiesen

Like many grammatical rules and issues, capitalization of the word “earth” is a complicated and somewhat muddied issue. The general consensus among grammarians and linguists is that the word should be capitalized when referring to the planet as a specific place in terms of astronomical reference, but can otherwise be lowercase even when referred to as a specific place. Whenever using the word to refer to soil or ground, the word should be written lowercase, but if writing something like “The Earth travels around the sun” it should be capitalized.

The names of planets, such as Earth, are capitalized because they are proper nouns.
The names of planets, such as Earth, are capitalized because they are proper nouns.

The general rule for capitalization of words in English is that a word should be capitalized at the start of a sentence, or if it is a proper noun. Nouns, typically, come in two forms: either common nouns or proper nouns. The typical explanation for what constitutes a noun is that it is a person, place, thing, or idea. In writing, common nouns should be written lower case, unless at the beginning of a sentence, and proper nouns should be capitalized.

When used to describe dirt or a mass of land as a general concept, the word "earth" is not capitalized.
When used to describe dirt or a mass of land as a general concept, the word "earth" is not capitalized.

Words such as “pencil,” “dog,” “school,” “nation,” “planet,” “religion,” and “teacher” are all common nouns. They describe a person, place, thing, or idea but are not precise or referring to a specific person, place, thing, or idea. In contrast, names like “Fido” or “Jonathan,” places such as “Iran” or “North Dakota,” things like “Empire State Building,” and ideas like “Supreme Court” or “Christianity” are proper nouns. They refer to a specific thing and are capitalized to reflect that fact.

The problem with the word “earth” is that it, along with a number of other words, can be used as both a common noun and a proper noun. When used to refer to soil, ground, or land, it's almost certainly a common noun, and should not be capitalized unless it is at the beginning of a sentence. “Earth” to indicate a place, however, is somewhat more complicated. In general, if it's being used to refer to the planet, but is not being used in an astronomical context, it should be written lowercase.

For example, if someone writes, “I wish for peace on earth, and good will toward men,” it should be written in lowercase. When “earth” is used to refer to a place in an astronomical context, however, then it is capitalized. So the same person could write, “I wish for peace on Earth, and war against Mars” and it would be accurately capitalized. The definite article “the” is often used before the word to indicate references to the specific planet as well, rather than to the ground or soil. This is often done to indicate that the planet is unique, though it is seldom mandatory and often depends on the flow of the words in the sentence.

The Empire State Building is a specific place and its name should be capitalized.
The Empire State Building is a specific place and its name should be capitalized.

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Discussion Comments


I think that regardless of what is proper, people will always hang onto their personal "capitalization of earth" views. I know many people who stick to whatever they made a habit of doing in high school, and though their grammar may be incorrect, old habits are hard to break.

Unless a person has a writing or editing job, their mistakes in this area may never be called to their attention. Everyone in general seems to be a bit fuzzy on the issue.


@kylee07drg - To avoid confusion, I always just say "soil" or "ground" if I'm referring to that meaning of "earth." I only use the word "Earth" when referring to the planet, and that takes the guesswork out of whether or not to capitalize it.


I've been doing it wrong all along! I never capitalize "earth."

To me, it has become such a common word that I don't ever think of it as a proper noun. I think that when a word can go either way like this, many people tend to forget that it sometimes needs to be capitalized. We just get so familiar with the word that we don't see it as important enough to be capitalized.


I think it's strange that you wouldn't capitalize earth in the expression "peace on earth." I mean, you're not talking about peace on the soil. You are referring to the planet as a whole.

It just makes things more confusing. I've always followed the rule that if you use "the" before "earth," then you don't capitalize it. Otherwise, you do.

Since I never say "peace on the earth," I always capitalize Earth in this instance. It may be wrong, but it makes sense in my mind, and I have to have some sort of structure to adhere to regarding this.


My English teacher taught us not to capitalize the word "earth" unless other planets are being mentioned and they are capitalized.

Some people say that the only time when earth shouldn't be capitalized is when you're talking about soil. Like if I said "I dug the earth to plant a flower."

But according to my teacher, that's not true. We don't have to capitalize earth even when we're talking about the planet. But if earth is being mentioned in a paragraph where other planets are also being mentioned and capitalized, then you have to capitalize earth too. So if you wrote something like "Pluto, Mars, Earth and Mercury," it should be capitalized.


@fify-- "The Moon is Earth's only satellite" is used in an astronomical context right? So "Earth" needs to be capitalized there. It's not necessary for "the" to be in front of "Earth" for it to be a proper noun. Even "Moon" is a proper noun here so it needs to be capitalized as well.

"Journal of Earth Sciences" also has to be capitalized. Not only does it have an astronomical context, but it's the name of the Journal.

"Planet Earth" is the same as the previous two examples, it needs to be capitalized. If you're talking about the program on BBC "Planet Earth," then there is no question about it being capitalized or not, it has to be.

And you're right, "Google Earth" is capitalized because it's the name of the program.


This is so confusing! I never capitalize earth and I had no idea that in some instances, it's supposed to be capitalized.

So if I wanted to say "the moon is earth's only satellite," should "earth" be capitalized here?

What about "earth" in "journal of earth sciences" or "planet earth?"

I only knew that "Google Earth" is capitalized but that's because it's the name of the program.


That's a good point aaaCookie. Proper grammar in sci-fi contexts can become tricky, and is usually used at the discretion of the writer since it may be dealing with word definitions not currently in common usage. You are probably correct, since "an earth" would imply one of multiple earths, at which point it is no longer a proper noun.


This article is very clear about the different ways to use the word "earth". One thing that I have also heard, at least in things like science fiction books and films, is the concept of "an earth", meaning a planet that can support life. This is not used often, but sometimes it is, and I imagine that it would not be capitalized as "an Earth" in this sense.

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