I'm quite fond of internal pluralisation, such as passers-by, mothers-in-law, or even Chambers of Commerce.

However, I've recently realised that I've no idea how to indicate possession in such a case.

Neither "Mothers-in-law's" nor "mothers'-in-law" seem right.

Is there a corrct way of doing this, or should it just be avoided?

  • 3
    My favourite internal pluralisations: Advocates General and Procurators Fiscal.
    – Seamus
    Commented Nov 2, 2010 at 12:52
  • 2
    ...and Directors General and Secretaries General. Commented Nov 2, 2010 at 15:46
  • I think I've found a paper on this! But I can't read it. Oh well. ncbi.nlm.nih.gov/pubmed/10214215
    – Rawling
    Commented Nov 2, 2010 at 16:14
  • 3
    What is that paper doing on PubMed anyway? Are there any health issues associated with building possessives?
    – RegDwigнt
    Commented Nov 4, 2010 at 16:20
  • @RegDwight: The paper is from "Nurse Author Ed", or the "Nurse, Author & Editor Newsletter". Commented Nov 4, 2010 at 16:36

2 Answers 2


"Mothers-in-law's" is a correct form. I am quoting the rule used in American grammar:

Also add an apostrophe followed by an s to the end of a singular compound noun that ends in any letter except s. For example:

  1. Queen of England's carriage
  2. King of Spain's castle
  3. Prime Minister of Canada's question
  4. mother-in-law's recipe
  • 2
    "Mother-in-law's" is clearly correct, but "mothers-in-law's" still seems wrong.
    – Rawling
    Commented Nov 2, 2010 at 13:09
  • 6
    I agree with your conclusion that “mothers-in-law’s” is the correct form. However, the rule which you quoted does not apply here because it explicitly states that it is about singular compound nouns. Commented Nov 2, 2010 at 13:32
  • 4
    "This is especially useful in pluralized compound structures: the daughters-in-law's car sounds quite strange, but it's correct. We're better off with the car of the daughters-in-law." grammar.ccc.commnet.edu/grammar/possessives.htm
    – Rawling
    Commented Nov 2, 2010 at 16:16

I suggest avoiding it. No matter how you put it, half of your audience will think you got it wrong and be distracted.

Try "the recipes of the mothers-in-law."

  • I agree that such possessives are usually best avoided: even though "the Queen of England's carriage" is grammatically correct, it is a bit ugly. Unless it is a usage hallowed by time or convention, I'd rephrase it as "the carriage of the Queen/King/Monarch of England (whichever is applicable)". Commented Feb 26, 2011 at 16:16

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