Learn Turkish: Arabalar pahalı mı? - Are the cars expensive?

The question particle follows 4-way vowel harmony based on the last vowel of the word before it. The last vowel in pahalı is ı, so the particle must be mı.

Where is the word for "are" in this sentence?

In Turkish, the verb "to be" (am, is, are) is often invisible in the present tense for the third person. You just put the subject (arabalar) and the adjective (pahalı) together, and add the question particle (mı) to make it a question.

Why don't we add a plural ending to "pahalı" since we are talking about multiple cars?

In Turkish, adjectives do not get a plural ending when they describe a noun. Only the noun gets the plural suffix (-lar or -ler). So we say arabalar pahalı, never arabalar pahalılar.

Why is "mı" written as a separate word instead of being attached to "pahalı"?

Unlike most Turkish suffixes, the yes/no question particle is always written as a separate word with a space before it. However, it still acts like a suffix by following vowel harmony with the word right before it.