‘Year Old' or 'Years Old': What's the Difference Between the Two?

By Shanea Patterson, updated on November 28, 2022

Is someone 10 ‘year old’ or 10 ‘years old’? How do you know which is correct? We’ll explain the correct usage of each phrase in more detail below. Plus, you’ll learn how to use the correct phrase in a sentence.

Don’t feel like skimming? The short answer is that both phrases are acceptable to use.

‘Year old’ would be used when modifying the noun that follows it or when the phrase is describing the age of a person, place, or thing. In this case, it would be hyphenated (i.e., year-old).

‘Years old’ is usually used to describe a person’s age only.

Is Year Old Hyphenated or Not?

So, should you use the hyphen when using the phrases ‘year old’ or ‘years old’? The hyphen should be used when it modifies a noun that follows it and when it’s describing the age of a person, place, or thing.

For example:

  • My two-year-old twins made a mess this morning. (correct)
  • My two-years-old twins made a mess this morning. (incorrect)

The ‘Year Old’ Hyphen: When to Use It and When to Drop It

As you can see, you’d only use the hyphen when it modifies the noun that follows it. And while you can use the hyphen with ‘year old,’ you’d never use it with ‘years old’ as it wouldn’t be grammatical.

Definition and Meaning

Before we get into examples of how to use both phrases in a sentence, let’s define both words.

The Merriam-Webster definition of ‘year’ is: “the period of about 365 ¼ solar days required for one revolution of the earth around the sun,” “the time required for the apparent sun to return to an arbitrary fixed or moving reference point in the sky,” “the time in which a planet completes a revolution about the sun,” “a cycle in the Gregorian calendar of 365 or 366 days divided into 12 months beginning with January and ending with December.”

It’s also defined as: “a time or era having a special significance,” “12 months that constitute a measure of age or duration,” “the final stage of the normal life span,” and “ a period of time (such as the usually 9-month period in which a school is in session) other than a calendar year.”

A few phrases containing the word ‘year’ include:

  • Fiscal year
  • Financial Year
  • Academic year
  • Calendar year
  • First-year
  • All year round

The Merriam-Webster definition of ‘old’ is: “dating from the remote past: ancient,” “persisting from an earlier time,” “of long-standing,” “distinguished from an object of the same kind by being of an earlier date,” “having existed for a specified period of time,” “of, relating to, or originating in a past era,” “advanced in years or age,” “showing the characteristics of age,” and “experienced.”

It’s also defined as: “former,” showing the effects of time or use: worn, aged,” “no longer in use: discarded,” “of a grayish or dusty color,” “tiresome,” “long familiar,” “used as an intensive,” “used to express an attitude of affection or amusement.”

Some synonyms of ‘old’ include:

  • Aged
  • Ancient
  • Long-lived
  • Senescent
  • Aging
  • Elderly
  • Older
  • Senior
  • Geriatric

How to Use ‘Year Old’ in a Sentence Correctly 

Now that we know what both words mean let’s look at how to use ‘year old’ in a sentence in the unhyphenated and hyphenated forms.


  • My three-year-old loves Coco Melon and Paw Patrol.
  • Your six-year-old son hit my five-year-old daughter.
  • I have a six-year-old son and a ten-year-old daughter that live with their mom.
  • My eight-year-old is afraid of flies.
  • It’s our one-year wedding anniversary today.


  • My son is a year old today.
  • This TV was only one year old; how did it break?
  • That house is one year old; it was built last year.
  • This organization is one year old; it’s a startup.
  • This report is one year old; where are the updates?

How to Use ‘Years Old’ in a Sentence Correctly

Now that we know how to use the first phrase in a sentence let’s see how to use ‘years old’ in a sentence correctly.

  • My niece turns nine years old in November.
  • I’m turning 25 years old this coming December.
  • My son is turning five years old and going to kindergarten this fall.
  • She’s 10 years old, and she knows five different languages.
  • She’s only 19 years old, which is too young for a margarita.

Concluding Advice on ‘Year Old’ and ‘Years Old’ 

As you can see, you’d use ‘year old’ and ‘years old’ somewhat differently. While ‘year old’ can be hyphenated, ‘years-old’ usually isn’t hyphenated.

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Written By:
Shanea Patterson
Shanea Patterson is a writer based in New York and loves writing for brands big and small. She has a master's degree in professional writing from New York University and a bachelor's degree in English from Mercy College.

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