'Polar opposites' vs 'a polar opposite'

[Sasha Zino]

Cambridge English Dictionary offers an example of only the plural form of the idiom mentioned in the title of my post: 'Love and hate are polar opposites'.
See the complete article by the following link:

POLAR OPPOSITES - Cambridge English Thesaurus с синонимами и примерами

POLAR OPPOSITES - Синонимы, слова и примеры по теме | Cambridge English Thesaurus

dictionary.cambridge.org

In the Collins Dictionary it is possible to find the idiom in the singular form:

https://www.collinsdictionary.com/dictionary/english/polar-opposite

Is this grammatical difference conditioned by the variant of English: either British, in which the plural form of the idiom seems to be unlikely; or American, where the plural form of the expressions appears to be possible (I've reached this conclusion on the basis of the information provided in the Collins dictionary, the US publishing house)? If I'm mistaken in my speculations, please, let me know.

 

[emsr2d2]

I don't think I've ever used it in the singular. It's always "They're polar opposites".

 

[5jj]

It's not uncommon in the singular form. Normally one thing is the polar opposite of another. Here are some examples: polar opposite.

 

[Sasha Zino]

Thank you for the answers and useful references!

 

[emsr2d2]

Thank you for the answers and useful references!

You're welcome but please bear in mind that there is no need to write a new post to say "Thank you" to anyone. Simply hover over the "Like" button (which I can see you have found already), and choose the "Thanks" icon. It saves time for everyone.

 

[Tdol]

British, in which the plural form of the idiom seems to be unlikely

What's your reasoning behind this- we happily use plurals in BrE where AmE uses the singular. I am a BrE speaker and would happily use the plural, and can't think when I have used the singular.