Wondering when you should hyphenated the words “year old”? The answer is pretty simple: whenever the words are used as an adjective (as in “the 16-year-old driver”), they should be connected with a hyphen.

Read on for more on when and how to hyphenate “year old,” as well as when the hyphen isn’t necessary.

When to Hyphenate Year Old

“Year old” should be hyphenated when it modifies a noun that follows it. That is, when the phrase is describing the age of a person, place, or thing, and it precedes that noun in a sentence, then it should be written as year-old.

In such cases, a hyphen should also connect year old to the number that precedes it (for example, “20-year-old girl”).

Note that these rules apply regardless of whether words or numerals are used to convey the age.

Examples

  • The 100-year-old building did not survive last year’s storm.
  • The three-year-old was reunited with his mother.
  • My 25-year-old sister is getting married this spring.
  • Her 2-year-old cousin is sleeping.
  • His 95-year-old grandmother is coming for Thanksgiving.
  • The 12-year-old boy wanted to run away from home.

When the age itself is a noun, year old still needs to be hyphenated.

For example:

  • The 10-year-old was very loud.
  • For being a 5-year-old, she’s very independent.

When Not to Hyphenate Year Old

Year old should not be hyphenated when it comes after the noun it modifies (as in, “She is 12 years old”).

Examples

  • This building is 150 years old.
  • I was 20 years old when I moved abroad.
  • My father just turned 63 years old.
  • This wine is 4 years old.
  • The villages is hundreds of years old.

To Hyphenate or Not to Hyphenate?

That is the question. We’ve got the answers in our guide on how to use hyphens, as well as more on em dashes and en dashes.

Proper punctuation is key for clear, effective, and professional writing, so make sure you understand these basic rules!

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