What is the correct way to add a possessive to a plural word that does not end in "s"? Is it women's

What is the correct way to add a possessive to a plural word that does not end in "s"? Is it women's or womens'?

David Dreaming Bear, Horsethief Canyon, California US

• It's women's. The apostrophe goes after the s when the plural has an 's', ie "The houses' roofs are covered in snow". Because 'women' is already plural, when you add the possessive 's,' the apostrophe goes before it.

  Matthew Redgrave, London

• The former. Women's. Because 'women' is already plural, and is possessive. Ergo, you just add the apostrophe 's'. It would only be womens' if womens without the apostrophe was the plural of woman. Despite the fact "women's" is right, my spellchecker still doesn't like it. I think it makes more mistakes than I do...

  Katie Edge, London

• Women's

  Roger Thomson, Brighton

• Women's. The apostrophe for possessives was added by 18th-century grammarians who thought the possessive came from a lost form where it was provided by a separate word rather than a special genitive form (John's hat = John his hat; Johns' hats = Johns their hats). Slightly mad but we're stuck with it. It's women's, children's, men's ...

  Keith Mason, London, UK