Talking about age in writing may sometimes be tricky. In this Ed’s Elevenses blog post, we will look at various ways to deal with age—hyphenated or otherwise.
“Simon turns 21 today.”
How old is Simon?
✅ He is 21.
✅ He is 21 years old.
❌ He is 21-years-old.
When you are stating the age of someone (i.e., “Simon”) or something, do not hyphenate “year old”. In other words, when the age comes after the noun it describes, do not hyphenate it.
“His 28-year-old brother, James, gave him a ten-year-old bottle of whiskey as a gift.”
Now, “28-year-old” and “ten-year-old” are adjectives that describe the nouns “brother” and “bottle of whiskey” respectively, so a hyphen is used. As such, hyphenate the age when it is an adjective or when it goes before the noun.
Consider how old Simon is again, but let’s use hyphenation this time:
✅ He is a 21-year-old boy.
✅ He is a 21-year-old.
❌ He is 21-year-old.
❌ He is 21-years-old.
It is important to remember to never pluralise “year” in “-year-old”!
Now, let’s look at “He is a 21-year-old” which is also a correct way to describe Simon.
The age is hyphenated because it is a noun. The same can be said about Simon’s 28-year-old brother, James, who can also be described as “a 28-year-old”.
“Simon goes out with his friends to a party that is full of 21-year-olds.”
As explained earlier, the age is hyphenated in this sentence because it is acting as a noun. When we talk about the “21-year-old partygoers” (i.e., more than one), we pluralise “a 21-year-old” and make it “21-year-olds”.
Other solutions to the “year-old” problem
Here are some other common ways to deal with age in writing:
✅ The party is for people aged 21.
✅ The party is for people aged 21 years.
❌ The party is for people aged 21 years old.
“Aged” is an adjective defined as “Having lived for a specified length of time” by the OED. Therefore, the party is organised for people who have lived for 21 years (not years old).
✅ Simon is in his early 20s.
❌ Simon is in his early 20’s.
You do not need an apostrophe when you are talking about the years of a person’s life.
The same goes with the years of a century:
✅ Simon was born in the 2000s.
❌ Simon was born in the 2000’s.
To find out more about the three major (and one minor) usage of apostrophes, please read How to Use Apostrophes.
Summing up: “Years old” or “year-old”?
The simplest way to determine when to hyphenate “year old” (or indeed all the “old”s, like “week old” and “minute old”) would be to look for the position of the age in relation to the noun.
When the age comes after the noun, do not hyphenate “year old”:
✅ The baby is two months old.
❌ The baby is two-month-old.
When the age (i.e., an adjective) precedes the noun, hyphenate “year old”:
✅ An 800-year-old castle.
❌ An 800 years old castle.
When the age is a noun, use hyphens:
✅ He is lying on the floor like a three-year-old.
❌ He is lying on the floor like a three years old.
Edison Tam MA MCIL CL is a Translator, Proofreader, and Copyeditor (zh-hk/en) who works with students, independent non-fiction writers, academic researchers, and clients from businesses and organisations of all sizes.
He is Chartered Linguist and Member of the Chartered Institute of Linguists (CIOL), and has undergone wide-ranging academic training in Business, Modern Languages, and Applied Linguistics in Hong Kong, London, and Barcelona.
The Languaging Lab | 香港翻譯校對服務 