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

The Quick Answer
Our moon is called The Moon, and our star is called The Sun. Therefore, when referring to our moon, use The Moon or Moon. When referring to our sun, use The Sun or Sun.

Capital Letters, 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 of our solar system is called The Sun. Therefore, the words to denote our moon and our 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.)

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