Learn Turkish: Öğrenci kütüphanede kitap arıyor mu? - Is the student looking for a book in the library?

When a verb ends in 'a' or 'e' (like ara-), that final vowel changes when you add the present continuous suffix. The suffix starts with a vowel (-ı, -i, -u, or -ü), so to fit vowel harmony, the 'a' in ara- changes to 'ı', making it arıyor.

Why is the question particle mu written as a separate word, and why did it take that exact form?

In Turkish, question particles (mı, mi, mu, mü) are always written with a space before them. However, they still follow the 4-way vowel harmony rule based on the word right before them. Since the last vowel in arıyor is 'o', the particle must be mu.

Why is it just kitap instead of bir kitap (a book)?

When a noun is placed right before the verb without any suffixes, it acts as a general, indefinite object. So kitap arıyor translates well to 'looking for a book' or the general action of 'book-searching.' If the student was looking for one specific book, it would take a specific object suffix: kitabı arıyor.

What does the -de suffix do in kütüphanede?