1.nà ér/nàr
there
我住那儿 I live there
that
那儿是我家 That's my home
someone's house
去我那儿怎样? What about go to my place?
since then
自打那儿起,我爱上了你 Since then,I have fallen in love with you
2.nǎ ér/nǎr
It seems only used in Taiwanese Manderin,but it should be 哪儿 but no 那儿 in Mainland China Mandarin
where
你在那儿? where are you?
the modest word of "no",When someone says something nice to you,you can use it out of politeness in a Chinese way