The Smiths decided to move to the country so that they could live in peace and quiet.


Is "and quiet" optional in the above? Thanks.
No. Peace and quiet is an idiomatic phrase meaning 'away from noise and activity; away form the hurly-burly'. Merely using 'live in peace' suggests that the Smiths are in danger, or are being persecuted or bothered elsewhere.
Hi Angliholic

"Peace and quiet" is an extremely common collocation. To me, the word 'quiet' is an important part of the description. So, for those two reasons, I would not consider 'and quiet' to be optional.

Oops, I see MM was much faster than I was. His description of how the word 'peace' (alone) would be interpreted is just right.
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Thanks, Mister.

Got it.
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And thank you, Amy.