Can someone please explain the correct way of pluralising month, for instance why do we sometimes use months or month, such as:

"Victor is a 7 month old baby"


"Victor is 7 months old"

What is the grammar behind this?


2 Answers 2

  1. '7 month old' is actually '7-month-old'. It serves as an attribute that modifies a noun. (e.g. old in the old dog.)

    It is adjectival and therefore has no plural form. You need to put an article in front of it and a noun after it.

    For example: He is a 7-year-old boy.

  2. 'is 7 months old' is a predicate that states something about the subject. (e.g. old in the dog is old.)

    In this case, adding -s to the end of year is the proper and regular way.

    For example: The boy is 7 years old.


Victor is a 7 month old baby.

In that case, 'a' acts as a determiner before the term '7 month'.

But in this one, '7 months' itself acts as a determiner.

Victor is 7 months old.

  • 1
    No, the predicate is not a determiner in your second example.
    – tchrist
    Oct 7, 2016 at 13:20

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.