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Some idioms related to common beliefs are "seeing is believing," "take it with a grain of salt," and "have faith." These idioms reflect the idea that belief is often based on personal experience, skepticism, or trust.
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Yes, some similar idioms include "two peas in a pod", "two birds of a feather", and "two sides of the same coin". These idioms all convey the idea that two things are closely related or have complementary qualities.
There are many idioms and phrases for 'on the back burner'. Some idioms and phrases for 'on the back burner' include 'pushing aside' and 'procrastinating'.
"Idioms for Being Afraid", "Idioms for Being Angry", "Idioms for Being Happy" are some examples of idioms found in the book "Found" by Margaret Peterson Haddix.
You can use a dictionary of slang and idioms, you can look online using a search engine, or you can check out the WikiAnswers related questions below!
Here is a link to some idioms. You can pick the "non-common" ones for yourself -- some people have heard certain idioms a lot and others have not heard the same ones, so you'll need to decide that part.
Some websites that have idioms written in them include The Free Dictionary, Cambridge Dictionary, and Phrases.com. These sites provide definitions and examples of idioms to help users understand their meanings and usage in context.
savvy, brainy
I'm not sure what fiction you mean. The word "fiction" is not an idiom -- it's a word and you can look in a dictionary to find it's meaning. There are too many idioms in works of fiction to name here. Click the related link to see some idioms.