Are there any cases where the plural and singular form of an English compound word or noun phrase differ in the number of words contained?
In all cases I can think of, the actual words within the noun phrase will change based on the grammatical number, but the number of words will not.
Examples,
large red car
becomeslarge red cars
in plural form. Both phrases have 3 wordsthis apple
becomesthese apples
– 2 words in each form
Are there any cases where the number of words will be different?
Background: I'm writing an app that performs basic natural language processing and, if my hypothesis is true, I can simplify its implementation significantly.
Best Answer
The answer appears to be no, there aren't any such plurals. The comments section on the question have pointed out a few interesting cases but they don't apply to the specific requirements you were looking for:
One additional exception would be adjectives that become invalidated when there are two:
But since your restriction appears to be of the form
[0-9] [noun]
I think you can escape these.The only evidence I have to offer on my behalf is Wikipedia's article on plurals and their extensive irregularities section. Nothing I saw on the article had an example of what you were looking for.
If anyone happens to come across an example I am more than willing to update the answer. In the meantime, I think it is safe to say that there are no such plurals -- and if there are they are extremely rare cases.