Capital Letters for the Sun, the Moon, Stars, and Planets

Our Story
The Quick Answer
Our moon is called "The Moon," and our star is called "The Sun."

When referring to our moon, use "The Moon" or "the Moon." When referring to the star that we orbit, use "The Sun" or "the Sun."
do you capitalize sun and moon?

Capital Letters with The Moon and The Sun

Like all proper nouns, the names of moons, stars, and planets are written with capital letters.

However, confusion arises because the name of the moon orbiting Earth is called "The Moon," and the sun, more accurately the star, of our solar system is called "The Sun." Therefore, the words moon and sun can be either proper nouns or common nouns depending on context.

Examples:
  • The largest moon orbiting Jupiter is Ganymede.
  • (In this example, the word "moon" is a common noun. However, "Ganymede" (the name of that moon) is a proper noun.)
  • The moon orbiting Earth is called The Moon.
  • (Here, the first "moon" is a common noun, but "The Moon" (the name of our moon) is a proper noun. That's why it has a capital letter.)
  • Are all suns as hot as The Sun?
  • (Here, "suns" is a common noun, but "The Sun" (the name of our sun) is a proper noun. That's why it has a capital letter.)

There's Only One Sun!

Even though people regularly use "star" and "sun" interchangeably when discussing astronomy, only our star is called The Sun. Therefore, it could be argued that the word "Sun" should always be capitalized because it is always a proper noun. While this is a fair point, too many people use "sun" as a common noun in place of "star" to declare this as a 100% rule. For example:
  • If you want to shine like a sun, first burn like a sun. (Former President of India APJ Abdul Kalam)
  • Benjamin Franklin maintained that every star is a sun, and every sun nourishes a 'chorus of worlds' just like ours. (Author Matthew Stewart)
  • And suns grow meek, and the meek suns grow brief, and the year smiles as it draws near its death. (Poet William Cullen Bryant)
We have not marked the examples above as right or wrong, but most astronomers would prefer the word "star" instead of "sun."

As a general rule, if the word "sun" is preceded by the article "the," then it is being used as a proper noun and should be capitalized. For example:
  • When The Sun comes up, I have morals again. (Comedian Elayne Boosler)
  • Stand a little less between me and The Sun. (Greek philosopher Diogenes)

Common Nouns and Proper Nouns

The following analogy might help with understanding the difference between common nouns and proper nouns:

Imagine you had a dog called "Dog."
  • I'm going to take Dog for a walk.
  • (Here, "Dog" is his name. It's a proper noun.)
  • I'm going to take the dog for a walk.
  • (Here, "dog" is what he is. It's a common noun.)
Read more about proper nouns.
Read more about common nouns.

Why Is There a Capital T on "The"?

When a name starts with "The," it should be written with a capital letter (e.g., The Sex Pistols, The Beatles). However, there is a lot of leniency on this ruling, particularly with regard to "The Sun" and "The Moon."
  • Does the Moon invoke romance?
  • Does The Moon invoke romance?
Read more about capitalizing "The" on the page about articles (see Issue 2).
Interactive Exercise
Here are three randomly selected questions from a larger exercise, which can be edited, printed to create an exercise worksheet, or sent via email to friends or students.

See Also

What are proper nouns? What are common nouns? Capital letters in advertisements Capital letters for the seasons Capital letters and the points of the compass Using capital letters with proper and common nouns Capital letters start sentences What is title case? Test on using capital letters