They are used for answering yes/no questions. Practically, you can use them alternatively. In fact, meanings of these words are a bit different: HAYIR (=no) X EVET (=yes) YOK (does not exist) X VAR (=exists) I believe the nuance between them, is not very important. Mainly, using `Yok` instead of `Hayir` or vice versa is more accurate in some situations. But i really believe that, if you are answering a yes/no question, you can use them alternatively: - Araban var mı? (=Do you have a car?) - "Evet, var" or "Evet" or "Var" (=yes, i do) - "Hayır, yok" or "Hayır" or "Yok" (=no, i don`t) - Ödevini yaptın mı? (= Did you do your homework?) - "Evet" or "Evet, yaptım" (=yes, i did) - "Hayır" or "Hayır, yapmadım" or "Yok, yapmadım" or "Yok"

hayır and yok(informal:yo) hayır:no there is/are not=yok have/has not=yok i havent a car=arabam yok there arent a book in table=masada bir kitap yok ....

'Hayır' simply means 'no'. 'Yok' means 'not present' or 'inexistant'. (as var is 'fee' in arabic, yok is 'ma-feesh') The word yok can be used instead of 'hayır' but I wouldn't recommend it.