Know Your English (Sep 2001)

Know your English

What is the plural of "mother-in-law"?

At the beginning of this century there was only one plural for this word - mothers in law. The word "mother in laws" was considered unacceptable. As a result, we had "fathers in law", "brothers in law", "sisters in law", etc.
Of late, native speakers of English have started saying, "mother in laws", father in laws", "brother in laws", etc. So to get back to your question, the plural of "mother in law" could be either "mothers in law" or "mother in laws". Take your pick.


Source:
The Hindu daily, Tuesday, September 04, 2001