I´m wondering if anyone would be able to help me. Okay so I know that if someone is older than you then you call then abi or abla etc but what happens in the case if you don´t know if they are older? and also when is it okay to use abi or abla. I mean to use abi or abla do they have to be close friends or friends you know well or can that be anyone who is older than you? 

I have a few people on my facebook account who I know they are older than me but have only just recently added them. We have converations but how would I addres them? would it be acceptable for me to say abi or would I say *** bey? 

thanks for anyone who can clarify

Leyla

You can say abi or abla to everyone, it is polite word. You can can call your brother/sister, friends or stranger. if person is much older than you, than you will say teyze to older woman and amca to older man. Also you can use kardeş for younger person.

It depends on your relationship with him/her. If you feel closer your self to him/her you can call abi (ağabey)/abla. If not keep going on to call them bey/hanım.