Question Sentences
Question sentences in Turkish can be classified into two groups like in English:
Yes-no questions
Regular questions
There are also question tags, i.e. questions of the form "You are coming, aren't you?".
In this lesson, we will see how these different types of questions can be asked in Turkish.
Before looking at how questions are constructed, let's see the question words in Turkish.
English Turkish
what? ne?
who? kim?
which? hangi?
where? nere?
when? ne zaman?
how? nasıl?
how many? kaç tane?
how much? ne kadar?
how often? ne sıklıkla

Now, let's see how different types of question sentences can be constructed.
1. Yes-no questions
In Turkish, yes-no questions are constructed with the question suffix '-mi'. It is important to note, however, the question suffix -mi is written separate from the word it is appended to. You can ask at this point: "Why is it a suffix instead of a separate word if it is written separately?". The reason question suffix -mi is regarded as a suffix is that it has to satisfy the major and minor vowel harmony rules for the word it is appended to. Let's see some example sentences demonstrating the use of the question suffix -mi.
A. This is a book. --> Bu bir kitap.
B. Is this a book? --> Bu bir kitap mı? (Note how the regular sentence is turned into a yes-no question sentence by the addition of the question suffix -mi)
A1. Yes, this is a book. --> Evet, bu bir kitap.
A2. No, this is not a book. This is a notebook. --> Hayır, bu bir kitap değil. Bu bir defter.

A. His name is Ahmet. --> Onun adı Ahmet.
B. Is his name Ahmet? --> Onun adı Ahmet mi?
A1. Yes, his name is Ahmet.
A2. No, his name is not Ahmet. His name is Mehmet. --> Hayır, onun adı Ahmet değil. Onun adı Mehmet.
A3. No. His name is Mehmet. --> Hayır. Onun adı Mehmet.

A. This is my house. --> bu benim evim
B. Is this your house? --> Bu senin evin mi?
A1. Yes, this is my house. --> Evet, bu benim evim.
A2. No, this is not my house. This is my mother's house. --> Hayır, bu benim evim değil. Bu annemin evi.

2. Regular questions
Regular questions are the ones constructed using the question words listed above and the answers to these questions are not simply yes or no. In English, there is a certain word order for regular question sentences. The question word comes first, and the rest of the sentence elements follow it. In Turkish, however, questions are constructed in a quite different way. To learn how to construct a question, a simple way is to follow the following steps. This will work in most cases:
Construct the answer sentence.
Locate the word or phrase that is the actual answer to the question.
Just replace that word or phrase with the appropriate question word.
Let's apply this on an example. The question we want to ask is, "Who is this?".
The answer sentence will be something like "This is my brother. --> Bu benim kardeşim."
The answer to the question is the phrase "my brother --> benim kardeşim".
Replace this phrase with the question word "who --> kim" and the question sentence becomes "Bu kim?".
To summarize, a question sentence has the same word order as a regular sentence. The difference is that the part of the sentence that is asked is replaced by the appropriate question word. The question word takes all the suffixes of the word it is replaced for.
Consider the sentence "Ahmet eve gidiyor. --> Ahmet is going home."
Who is going home? --> Kim eve gidiyor? (Ahmet in the regular sentence is replaced by who. The rest of the sentence is the same.)
Where did Ahmet go? --> Ahmet nereye gitti? (ev in the regular sentence is replaced by nere. Note that the question word nere also takes the suffix -e of the word ev and becomes nereye, meaning 'to where')
What is Ahmet doing? --? Ahmet ne yapıyor? (The phrase 'eve gidiyor' in the original sentence is replaced by "ne yapıyor --> what's he doing")

Note that to make a question sentence asking a verb, we use :
"What + to be (in the appropriate tense) + object + to do (in the appropriate tense)"
Ex1: What are you doing?
Ex2: What did Ahmet do?
In Turkish, this structure becomes:
"Object + ne + yapmak (in the appropriate tense and person)"
Ex1: (Sen) ne yapıyorsun?
Ex2: Ahmet ne yaptı?
This is simply the regular sentence where the action is replaced by "ne + yapmak", which is consistent with our rule for constructing question sentences.

3. Question tags
Question tags are the questions of the form:
You are home, aren't you?
He did his homework, didn't he?
Mehmet will come today, won't he?

Constructing question phrases in Turkish is very simple and straightforward. You just add "değil mi" at the end regardless of the sentence. The translations for the question tags above are then:
Evdesin, değil mi?
Ödevini yaptı, değil mi?
Mehmet bugün gelecek, değil mi?