Types of questions

There are two major types of questions in Bulgarian:
1. questions containing an interrogative pronoun (e.g. кой, какъв) or an interrogative adverb (e.g. кога, защо) – the so-called special questions or wh-questions;
2. questions containing an interrogative particle (e.g. ли, нали) – the so-called yes/no questions or closed questions.

Since the interrogative pronouns and the interrogative adverbs function as a sufficient “signal” that we are asking a question, the word order of the questions is quite flexible. This is in stark contrast with English, where the interrogative pronouns and the interrogative adverbs can function as relative pronouns and relative adverbs:
Кой дойде вчера?Who came yesterday?
Мъжът, който дойде, е брат ми. – The man who came is my brother.
Къде ходиш след училище?Where do you go after school?
Там, където ходиш, е опасно.Where you go is dangerous.

The interrogative pronoun/adverb can be moved to the middle of the sentence without hindering understanding:
Къде живее Мери? = Мери къде живее? (Where does Mary live?)
Какво е това тук? = Това тук какво е? (What is this here?)
The second examples in which we have moved Мери and това тук to the beginning of the sentence imply that they bear the logical stress, so a more precise rendering of their meaning in English would be “Where does Mary (and not someone else) live?” and “What is this here (as opposed to anything else)?”

It has to be noted, however, that in everyday conversations such placing of the question word will not always indicate that the emphasis has been placed on the sentence element that was moved to the front. Thus, depending on the intonation, sentences like
Том кога ще дойде? (When will Tom come?)
Тим защо е дал книгата на Джейн? (Why has Tom given the book to Jane?)
can be interpreted as neutral and practically equivalent to the respective English questions.

It is even possible to place the question word at the end of the sentence in order to express incredulity, irritation or surprise (accompanied with sharply rising intonation usually uncharacteristic of this type of question):
Том ще дойде кога? (The speaker is either incredulous or irritated by the time of Tom’s arrival)

Questions containing interrogative pronouns

Кой е най-добрият ти приятел?Who (masculine) is your best friend?
Коя е най-добрата ти приятелка?Who (feminine) is your best friend?
Кое е най-красивото момиче?Who (neutral) is the most beautiful girl?
Кои са най-красивите момичета?Who (plural) are the most beautiful girls?
Какъв вестник четеш?What (masculine) newspaper are you reading?
Кой вестник четеш?Which (masculine) newspaper are you reading?
Какъв искаш да стенеш?What (masculine) do you want to become?
Каква музика слуша той?What (feminine) music does he listen to?
Какво обичаш да правиш?What (neutral) do you like doing?
Какви обувки имаш?What (plural) shoes do you have?
Чий е този стол?Whose (masculine) is this chair?
Чия шапка е това?Whose (feminine) hat is this?
Чие дете плаче?Whose (neutral) child is crying?
Чии родители ще дойдат?Whose (plural) parents will come?
Кого познавате?Who(m) do you know?
Кому/на кого помагате? – (кому is an archaic form, commonly replaced by на кого nowadays) Who(m) do you help?
Що е то? (що is an archaic form, commonly replaced by какво nowadays) – What is it?
Колко приятели имаш? How many friends do you have?
Колко кафе пие тя?How much coffee does she drink?

Questions containing interrogative adverbs

Къде учи Том?Where does Tom study?
Кога ставате?When do you get up?
Как направи това?How did you do this?
Защо дойдоха?Why did they come?

Questions containing interrogative particles

The most commonly used interrogative particle in Bulgarian is ли. Ли is usually placed directly after the word that is the logical focus of the question (the word being emphasized, the word which will be confirmed or negated in the answer):
Ще вали ли? – Will it rain?

The interrogative particle ли isn’t itself stressed, but the word preceding it is pronounced with a raised voice:
Петър ли вчера донесе книгите?Was it Peter who brought the books yesterday?
Петър вчера ли донесе книгите?Was it yesterday when Peter brought the books?)
Петър книгите ли донесе вчера?Was it the books that Peter brought yesterday?
Петър донесе ли книгите вчера? – Did Peter bring the books yesterday (as opposed to keeping them)?

Note that when the particle ли asks about the verb, the verb (together with the particle ли) tends to be placed in the middle of the sentence (rather than at the end) if there is another (one or more) secondary part of the sentence present (Петър донесе ли книгите вчера?) and usually stands at the end of the sentence only if there are no secondary parts to accompany the verb (Ще вали ли?).

Other interrogative particles are: дали, нали, нима, да не би да, а, е, and the archaic мигар, зер:

Дали ще вали? – Will it rain, I wonder?
Нали ще ми кажеш? – You will tell me, won’t you?*
Нима не знаеш? – (to express surprise) Don’t you know?
Да не би да знаеш отговора?Do you happen to know the answer?
А? Какво каза? – (as a colloquial substitute for Pardon?) Eh? What did you say?
Утре заминаваш, а? – (as a colloquial substitute for нали) – You are leaving tomorrow, aren’t you?
E? (or Е, и?, or И? ) – when we are urging the interlocutor to continue speaking

*Нали is used as an equivalent of the so-called tag questions, but, unlike English, its position in the sentence isn’t fixed:
Tom is working in the garden, isn’t he?
Нали Том работи в градината?
Том нали работи в градината?
Том работи в градината, нали?

Tim arrived at the airport early, didn’t he?
Нали Тим пристигна на летището рано?
Тим нали пристигна на летището рано?
Тим пристигна на летището рано, нали?

Questions containing interrogative pronouns/adverbs and interrogative particles

Bulgarian question can contain both an interrogative pronoun or adverb and an interrogative particle. They usually express uncertainty, hesitation, exasperation, etc:
Кой ли ще дойде? – Who will come? (the speaker is uncertain that anyone will come)
Защо ли те питам? – Why am I asking you? (shows exasperation or impatience)
Къде ли са отишли? – Where have they gone? (the speaker has no idea where they might have gone)

Other types of questions

As is the case with multiple other languages, a question can be formed by just using interrogative intonation with a declarative sentence, or even a single word:
Иван ще дойде? Сега? – Ivan will come? Now?

We can also have questions such as:
Петър ли ще дойде, или Ана? – Will Peter come, or Anna?

We can ask a question based on another question, and in this case there will be two question words or a combination of a question word and a particle:
A: Кой ще ти помогне? B: Как кой ще ми помогне? (А: Who will help you? B: How come who will help me? – to express doubt as to the general legitimacy of the first question).
A: Кога е дошъл Том? B: Том ли кога е дошъл? (А: When did Tom come? B: Is it Tom’s arrival that you are asking about? – to clarify some part of the first question)

Пашов, Петър. Българска граматика. Пловдив, Изд. къща “Хермес”, 2005
Бояджиев, Тодор, Иван Куцаров и Йордан Пенчев. Съвременен български език. София, Изд. къща “Петър Берон”, 1999