Which way is more natural when it comes to numbers of things that people have or own? For example, the numbers of cars owned by households:

The rate of single/dual/triple-car households is increasing.

The rate of one/two/three-car households is increasing.

I feel like cardinal numbers are only suitable when you talk about parts of a system or machine:

a two-wheel vehicle

a one-way ticket/street

a three-way tie between A City, B City and C City

a five-year plan presented to the cabinet

When it comes to people with agency, ownership or possession, I feel like the adjectives single, dual, triple, etc. are more appropriate

a dual-citizenship individual

a single-income family

But then there are also cases where no humans are involved like:

a single/dual-core CPU

So how do you determine which cases to use numbers and which to use adjectives in attributive forms?

  • Google Ngrams suggests one-car family is much more common than single-car family, and doesn't like double-car at all. I don't think there's a general rule; use what other people say if you're responding to their research or they ask you to work, and realise it doesn't matter too much.
    – Stuart F
    Mar 22 at 9:32
  • 1
    Double-decker, triple treat, quad-rotor drone. Your sense of how this works is wrong. When the number is a free option, go with the number. It is usually highly restricted when attributives are trotted out.
    – Phil Sweet
    Mar 22 at 9:38
  • @StuartF Your search seems to be faulty. Look at the error messages " Replaced one-car family with [one - car family] to match how we processed the books. info Replaced single-car family with [single - car family] to match how we processed the books." Normally there should be actual results, but here there are no citations that perfectly match the spelling "one-car" or "single-car" (without spaces) Mar 22 at 9:56
  • @StuartF I skip the word "family" and got completely different graphs, again with no citations whatsoever. I don't think Ngrams Viewer is the best tool for this kind of search. Mar 22 at 10:00
  • @StuartF If Google Books treats "one-car" as two separate words, not a compound, then it's no wonder there are more results for "one car". There's simply no way "single" could be more common than "one". Mar 22 at 10:15


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