The reason is the rule of the question suffix. 1. It's always written separately from the previous word. 2. It's written next to the personal endings. Examples: - Ben yaparım. ~ Ben yapar mıyım? <ENG> I do. ~ Do I do? - Sen yaparsın. ~ Sen yapar mısın? <ENG> You do. ~ Do you do? - O yapar. ~ O yapar mı? <ENG> He does. ~ Does he do? - Onlar yaparlar. ~ Onlar yaparlar mı? <ENG> They do. Do they do? As you can see the personal endings are next to the question suffix. But in your example there is a plural suffix ("lar, ler") also. Maybe you know "they" is "Onlar" in Turkish. It is a plural form of "he/she", "o" in Turkish. So we don't add plural suffix to the question suffix. Thus, your example is like that. Your examples: - Bira içerler. ~ Bira içerler mi? <ENG> They drink beer. ~ Do they drink beer? - Börek yersin. ~ Börek yer misin? <ENG> You eat börek. ~ Do you eat börek?

Teşekkürler Tulay, I'm trying to understand it.. :)

the reason is about the subjects that you used. in the first sentence subject is 'they'. that is why you say bira içerler mi ler is used for plural nouns. However, in the second sentence the subject is 'you'. therefore you should say bira içer misiniz. miyim misin mi miyiz misiniz miler

yersiniz mi is completely wrong. it is always yer misiniz. Bira içer misiniz. is correct, but bira içersiniz mi is completely wrong.