Compound words/noun phrases in english with different number of words in plural/singular form

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 becomes large red cars in plural form. Both phrases have 3 words
• this apple becomes these 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.

Solution 1:

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:

numerical counts: one car => two hundred cars

article removal: a car => cars

collective nouns: a sheep => a flock of sheep

One additional exception would be adjectives that become invalidated when there are two:

a single wolf => two single wolves

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.