what does "vernacular" mean?

2 New York Times headlines today

Rochester Police Chief Resigns After Accusations of Cover-Up in Prude Case

Dallas Police Chief Resigns in Wake of Policing Protests

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     Ah! -- when I review Raymond Chandler's books, especially The Big Sleep, it's a transporting experience because of the unique, haunting mood he creates with his writing.

     ------------ Thunder was crackling in the foothills now and the sky above them was purple-black.  It was going to rain hard.

*       *

     ----------- The Sternwoods, having moved up the hill, could no longer smell the stale sump water or the oil, but they could still look out of their front windows and see what had made them rich.  If they wanted to.  I didn't suppose they would want to.

     Thoughts and observations and speculation are all layered in, so seamless that the reader might feel like he thought of all this himself....

---------------- She walked with a certain something I hadn't often seen in bookstores. ...

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     Reading analyses of Chandler, we come across the word "vernacular" more than once... What does it mean?

Merriam-Webster:

vernacular --

using a language or dialect native to a region or country rather than a literary, cultured, or foreign language

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     In the brief Big Sleep reading of the past week, one encounters references to material things that are flimsy and unreliable:

------------------ The rain drummed hard on the roof of the car and the burbank top began to leak.

-------------- About the only part of a California house you can't put your foot through is the front door.

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-------------------------- Neither of the two people in the room paid any attention to the way I came in, although only one of them was dead.

...big houses in ghostly enormous grounds...like witch houses...

I was as wet as I could get already.  And on a night like that you can grow a beard waiting for a taxi.  And taxi drivers remember.

     Three reasons not to call for a taxi...

This stuff is all about the atmosphere, and bringing the reader -- in.  So that you're telling part of the story yourself....

----------------- I went through the house again....

Geiger wasn't in his flounced bed

or under it 

or in his closet....

That left the locked door on the right of the hall.  One of Geiger's keys fitted the lock.  The room inside was interesting, but Geiger wasn't in it.  It was interesting because it was so different from Geiger's room.

     It was a hard bare masculine bedroom....

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