I know that compound nouns can be made up of two or more words and linked using a hyphen. My 3-year-old apple-pie (boy) always asks me "What is it?" and sometimes "What is this/that?" and it's really annoying.

I wish to use the compound noun "what-is-it" in the plural form and say:

  • I'm so tired of his what-is-its.

Is this the correct plural form for such a compound noun?

I'm confused since different compound nouns are pluralized differently.

  • mother-in-law = mothers-in-law
  • court-martial = courts-martial or court-martials (both are accepted)
  • forget-me-not = Forget-me-nots
  • filler-in = fillers-in
  • run-in = run-ins

Does "what-is-it" change according to the first rule - When a noun is hyphenated with a preposition, the plural is formed on the noun or second rule - When neither word of a compound is a noun, the plural is formed on the last word?

  • 2
    Since you mean his utterance "What is it?", not a compound noun a "what-is-it", I would simply stick "s" at the end. No matter what the utterance, I would probably pluralize it that way. "I'm so tired of his I'm-just-going-to-be-gone-for-a-minute-s. It always means he'll be out half the day." On the other hand, if you were using it like a noun, such as "Dad, have you seen my whatsit?" then I might pluralize it either as "Dad, have you seen my what're-they(s)?" Or "Dad, have you seen my whatsits?" Since it's child language, the rules are likely to be bent in any case. Jul 5, 2017 at 15:59
  • @LukeSawczak So I could use "what-is-it-s", "whatsits", and "what-is-its" interchangeably? Jul 5, 2017 at 16:16
  • 1
    If he says "What is it?" and it's this utterance that you're tired of, I would probably write: his What-is-its. But quoting speech like that is mostly done orally, so there isn't a very solid convention, to my knowledge. (A close parallel might be: "No ifs, ands or buts.") Jul 5, 2017 at 16:27
  • I would not use it here. When I ask a question of a person and point at an object (just like a little child), I would say; "What is this?" or "'What is that" or the abbreviated forms but not: 'What is it? |What is it| is what a mother says to a child who is being annoying: What is it, Johnny? What's the matter? So: What-is-it questions or What-is-that questions. And forget making a noun of it. These hyphenations are used adjectivally, rather than as nouns.
    – Lambie
    Jul 5, 2017 at 19:31
  • @Lambie That's too complex. And he does ask What is it? What is this? What is that? But the first is easier to pronounce for a child. Jul 6, 2017 at 4:57

2 Answers 2


Since you are referring to plural of utterances and not plural of a preexisting compound noun, I would add the "s" to the end of the whole phrase, as you have instinctively done in your question. In this case the issue is that the phrase follows the pattern of compound nouns, but isn't one. "What is it" is not inherently a stand-alone noun like "mother-in-law" is; it is a sentence being artificially considered a noun as a whole.


Plural "concatenated compound nouns" such as mothers-in-law, courts-martial, fillers-in, passers-by contain a "head noun" - they're either clearly-identified types (of mother, court,...), or they're nouns followed by a preposition (in, by,...) that "contextualizes" the relevant noun. See here for more details.

It's something of an archaic hangover that with many such terms we still usually pluralize the head noun, rather than the whole expression. I've no doubt some people go out of their way to remember and make use of the pluralize the head noun principle primarily to show how "educated" they are. And there will be others who know perfectly well which is the "correct" form - but deliberately flout it to show contempt for those few usages that are out of step with the standard method (add s to the end of the complete noun phrase, regardless of any internal "structure").

Many people recognize the principle that words ending in -ful use the modern standard plural syntax (teaspoonfuls, handfuls) - but Google Books contains thousands of written instances of two teaspoonsful, handsful,... - which just goes to show that when the rules get too complicated, compliance falls off.

See this NGram showing how "pedantically correct" poets laureate is gradually being replaced by "naturally conformal" poet laureates. It's a long slow process, but the change is mostly in one direction.

In the case of forget-me-nots, merry-go-rounds,... there's no obvious head noun, so no-one is tempted to put the pluralising s anywhere other than at the end.

Finally, here's an interesting discussion re pluralization of Portuguese man o’ war (a type of jellyfish), where at least one "competent writer" chose to use the singular as the plural - the way we do with sheep and deer.

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