Years Old: Hyphen or No Hyphen?

/ Erin Servais
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 the founder of Dot and Dash, LLC, an author-services company focusing on women writers and offering a range of editing, coaching, and social media packages.

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36 thoughts on “Years Old: Hyphen or No Hyphen?”

  1. I thought you might also add to this post the variation of when we refer to a person by their age, without any other modifiers: “Only a ninety-year old would say such a funny thing.” Or, “I have two kids, a three-year old and a ten-year old.” I’m not sure the best way to articulate the rule, but I’ve done it correctly, right? Just checking.

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    • I think “a ninety-year-old,” while treated as a noun unto itself, is actually an adjective for a noun that has been dropped: “a ninety-year-old person.” The trailing noun can only be dropped because it is understood/implied, and goes without saying. But we would still hyphenate “ninety-year-old” as any other phrase with a noun coming after it.

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  2. In CP (Canadian Press) style, fourteen would be written as a number, as in: a 14-year-old hamburger (eating it is OUT of the question 😉 ). Does AP style not have the same guideline?

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    • You would hyphenate: “Even now, as a thirty-year-old [person, man-child, whatever]…”

      [Full disclosure: I am much older than thirty, and still like Lucky Charms.]

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  5. What if it’s in a series, as in one- two- and three-year-olds? Should there be commas to separate them as in one-, two-, and three-year-olds? It doesn’t look right. Or should it be written without the dashes as in one, two, and three-year-olds?

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  6. I have the same question as Kevin. It is my understanding that, when used as a noun, no hyphens are used. The fourteen year old at the donut. The fourteen-year-old girl at the donut. But I’m not sure and have been scouring the internet to find out. This site did not help!

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    • Despite advice to the contrary, there should be a difference between “one year old” and “one-year-old infant” In both cases, one year old and one-year-old are compounds, but only in the latter is it acting as a modifier to an external head noun. A general rule of English is that compounds do not hyphenate unless they are modifying an external noun. So we get:
      I like to eat ice cream (not ice-cream)
      I mad an ice-cream cake (not ice cream cake)
      Of course, all bets are off if the compound is adjoined, like blackboard.

      Going back to the age issue, in the case of “one-year-old infant” it is modifying the noun “infant” and so should be hyphenated, but for the simple: “He is a one year old” there is no external modification and it should be unhyphenated. Most websites will say that you should hyphenate both of these, but that does not follow the general rules of hyphenation in compounding. In case you might be wondering if it should be “one-year old” this is not the case because this is a headless compound. That is, “one year” is not modifying “old”. “Old” is not a head noun in this case, so there should be no hyphenation.

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      • I only agree with this argument to an extent, Peter. Your other examples aren’t the same. So yes, totally agree re ice cream and ice-cream cake. But the difference here is that “my one-year-old” is simply omitting the word child/baby/son/daughter (etc.) as shorthand. There is no such thing as a one-year-old per se, because, if I were a robot, I’d say, “a one-year-old what? You need a noun.” But in reality, we all know what is meant. So, by implication, the compound adjective is modifying a noun that isn’t there simply because of accepted (or vernacular, if you will) shorthand.

        Just to clarify, I would still advocate no hyphens in “My son is one year old”, because grammatically that’s different.

        And yes, one-year old is definitely wrong.

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        • Hi Ashley, I think your idea falls short because it does not generalize. That is, there is no rule or convention that nouns that are understood can be deleted. For example, one cannot say “I have a blue car and you have a red” — even though we all know that we are talking about a red CAR. In fact in the case of “year old” it is not clear what the head noun would have been — child/person/boy/girl. etc. Also, adjectives cannot be pluralized unless they are converted to nouns: “I have 3 blue cars and you have 2 reds”. Whereas, age-based compounds are themselves nouns and easily pluralize: “I have two 4 year olds in my class”. Therefore the most parsimonious analysis is that the “x year old” construction is a headless compound noun that is not modifying a noun itself (understood or not) and therefore by compounding-hyphenation rules should not be hyphenated. I should note that this goes against, for example, APA rules, which say you SHOULD hyphenate. But then again, those are not always written by people trained in linguistics and it’s something that I have been “corrected” on before much to my chagrin!

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  9. A ninety-seven year old woman
    A twenty-five year old man
    An eleven year old girl
    A seven year old boy

    A twenty-five year old man and his twenty-two year old wife
    A thirty-three year old woman with her seven year old son and eight year old daughter

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  10. What about a plural combination such as: the playground was dominated by 10- and 12-year-old boys.
    Is it correct to place a hyphen with the 10?

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    • Follow the same conventions as written numbers in general: that is, always spell out numbers less than ten (or, if you prefer, less than 100). So, you should always spell out “one-year-old toddler” but it’s up to you whether you write “16-year-old girls” or “sixteen-year-old girls.”

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  14. Thank you so much, in fact after 29 years and seven months living in this lovely land, this is the first time I’ve learned when to use year and years.
    Best regards
    Kaisy

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  17. Is the age describing a noun? Does the age precede a noun? If the answer is yes to these two questions, hyphenate. In the following examples, notice how the two conditions are met.

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