In formal research, which is more correct, and why:

  • the group of 40-50 years old OR
  • the group of 40-50 year olds

In any case the phrase in bold is to be treated as a noun only, as in:

The middle group of executives, ie. 40-50 years old is well balanced....

Without a range, the hyphenation rules I am used to would suggest "15-year olds" for instance. However "the 15-25-year olds ..." doesn't present well, does it?

There are related questions here, but none that seem to exactly address this topic. Eg.

Pluralization rule for "five-year-old children", "20 pound note", "10 mile run"

The main difference perhaps is that I need to use ranges, which already use a hyphen.

  • "The group of 40-50 year olds" is the noun phrase. The other is not. Why did you have a doubt? In the example sentence, the phrase serves as a qualifier for the noun executives before it, and as such it is also correct, though needs a comma after it.
    – Kris
    Oct 26, 2012 at 12:41
  • 2
    Incorrectly punctuated, and omit the "e.g.", which would normally be the verbosity (in this case) "i.e.". Should be: "The middle group of executives, those 40-50 years old, is well balanced...."
    – user21497
    Oct 26, 2012 at 13:39
  • 1
    You can use "the 15- to 25-year-olds ..." instead. That looks better.
    – user21497
    Oct 26, 2012 at 13:42
  • 1
    For ranges, en dashes are used, not hyphens.
    – RegDwigнt
    Oct 26, 2012 at 14:52
  • 1
    @BillFranke We have met the publisher, and he is us.
    – bib
    Oct 26, 2012 at 21:21

1 Answer 1


If you are using it as a compound adjective or noun, as in your example sentence, it should be "40-50-year-olds".

If you are using it as a separate qualifier, as in BillFranke's suggested alternate wording, than it would be "those 40-50 years old".

Confusing, perhaps, but the general rule is that when any sort of counted "thing" is used as an adjective, the object of the count is singular. "40-year-old man", "3-mile run", etc. Making it a range instead of a single number doesn't change that.

But when a number and an object of that number are used "on their own", i.e. not as a compound word, the normal rules of pluralization apply: "those 1 year old", "those 2 years old", etc.

  • Thank you; thus ranges shouldn't affect the compound-adjective dashing. One of the things I like about these SEs is that people tend to include references supporting answers, to be sure. I don't have one myself but remember from high school, and based on not letting ranges change things as you imply, that "40-50-year olds" should be correct, allowing a space to separate the adjective from the noun.
    – Marcos
    Oct 29, 2012 at 9:23

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