For example lets consider the name 'file system'. It consists of 2 nouns. Now, lets assume I want to use it in plural form. Which one of the following sentences is correct?

I have 5 file systems installed.

I have 5 files systems installed.

Is it like always one of them is valid, or maybe it depends on the context?

1 Answer 1


Context is not relevant. The correct version is always this:

I have 5 file systems installed.

The rule is that only one word of a compound noun gets a plural ending. In most cases, it is the last word. In a few rare cases, where the final word modifies the previous noun, the noun gets modified:

courts martial
*court martials

where court is the noun, and martial identifies the kind of court. As I said, these cases are rare. As far as I know, everyone memorizes them individually.

  • 1
    "everyone memorizes them individually"... Actually most people forget about them, which is why we get "secretary generals" and "poet laureates"
    – James K
    Commented Jul 31, 2021 at 10:46

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .