knowing idioms

know inside out

ex: she knows the system inside out

: meaning

she knows every detail of it

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know his/her stuff

ex : when it comes to geography,he certainly knows his stuff

: meaning

he has very good knowledge of it

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has a familiar ring to it

ex : that book title has a familiar ring to it. i think i read it a long time ago

: meaning

 it sounds familiar/i think I've heard it before

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rings a bell

ex : I'm not sure if i know her,but the name rings a bell

: meaning

i have a vague memory of some one with that name,but can't remember exactly