I belive it's technically accurate to say that

It is in John's interest that the cats are fed.

Where apostrophe+s is used to show John's possession of the interest

But why is is that

Undertaken in the public interest, investigative journalism involves original reporting.

does not use "public's" (i.e. with an apostrophe and 's' to represent possession)?

  • 3
    Public is being used adjectivally, like the popular vote, the common man, etc. Specifically, I'd say it's a noun adjunct usage. Sep 12, 2016 at 11:54
  • And like bank interest.
    – bib
    Sep 12, 2016 at 12:03
  • 1
    "Public's" would be legit, it's just that "public interest" is more idiomatic and is equally legit.
    – Hot Licks
    Sep 12, 2016 at 12:05
  • 1
    @FumbleFingers - Your examples aren't exactly equivalent, since "popular's vote" and "common's man" would not be used (at least not in the same sense). This is because they don't have noun senses. "Public" has both adjective and noun senses.
    – Hot Licks
    Sep 12, 2016 at 12:07
  • 1
    As an adjective Public is not being used as a possessive. Sep 12, 2016 at 12:51

1 Answer 1


"Public" can be either a noun. In this case it is an adjective, however:



of, relating to, or affecting a population or a community as a whole:
public funds; a public nuisance.

of, relating to, or being in the service of a community or nation, especially as a government officer:
a public official.

pertaining or devoted to the welfare or well-being of the community:
public spirit.

Additionally, "public interest" as a whole, is a noun:

public interest


The benefit or advantage of the community as a whole; the public good.

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