colloquialness

Dear to whom may it concern,
What does colloquialness mean?Is that of the same meaning with colloquy?
Would you please explain to me and make some examples?
Regards
Mitra584

It is the state/quality of being colloquial, though it is not a very efficient word, and wouldn’t be found in many dictionaries as the majority of people would refer to ‘being colloquial’ rather than ‘colloquialness’.

She wrote her letters in a colloquial style/way manner
would be preferable to
She wrote her letters in with colloquialness.

Dear beeesneees,
I have some more questions.
Is colloquy the root of colloquial?
If it is correct,
Colloquial means informal/familiar conversation but colloquy means literary conversation. There is contradiction between them.
Would you please explain it to me?
In advance accept my apology for being a talkative pupil.
Regards
mitra

There is no true ‘contradiction’ It is simply a complete difference in meaning. They are two separate words and although they share the same root word origin they don’t have the same definition.

Dear beeesneees,
Thank you vey much indeed.
Regards
Mitra