Years old: Hyphen or no hyphen?

Cake with a number three candle

This cake celebrates someone who is three years old. Photo by Annie Spratt on Unsplash

This post teaches when to hyphenate the phrases years old and year old.

Let’s take a look at two sentences:

His son is four years old.
He has a four year old boy.

In the first sentence, you would not use hyphens. In the second sentence, you would, making it four-year-old boy. This is because the phrase four year old is modifying the noun boy.

A good clue to determine whether you should hyphenate the year old phrase is to see if a noun comes after it. If there is a noun, hyphenate:

six-year-old toy
fifty-year-old whiskey
eight-year-old cat

If the sentence is simply stating that someone or something is so many years old, then don’t use a hyphen:

Her dad turned sixty years old today.
His baseball card is seventy years old.

Quiz
Determine whether the words in italics should be hyphenated. The answers are at the bottom.

1) Sasha is eight years old.
2) She has a three year old turtle.
3) Maddie is a five year old girl.
4) The painting is one hundred years old.
5) He ate the hamburger that was fourteen years old.
6) He ate a fourteen year old hamburger.

Answers:

1) not hyphenated 2) hyphenated; three-year-old turtle 3) hyphenated; five-year-old girl. 4) not hyphenated 5) not hyphenated 6) hyphenated; fourteen-year-old hamburger.

Erin Servais is a book editor and author coach. Learn more about working with her on your next project: dotanddashllc.com