Learn Farsi: آیا این یک سیب است؟

Yes, yek literally means the number 'one'. In Farsi, there is no separate word for 'a' or 'an'. Instead, the number yek is commonly used before a noun to show that it is indefinite, meaning just 'an' apple, not a specific one. So yek sib translates perfectly to 'an apple'.

Does Farsi have different words for 'a' and 'an' depending on the noun?

No. English uses 'an' before vowels and 'a' before consonants to make pronunciation smoother. Farsi does not do this. You simply use yek before the noun regardless of what sound it starts with.

Why is the verb ast (is) at the very end of the sentence?

In Farsi, the verb almost always comes at the end of the sentence. While English swaps the verb and subject to ask 'Is this an apple?', Farsi keeps its regular order and structures it like 'Question-word this an apple is?'.

Do I always have to use āyā to ask a yes/no question?

No, it is not strictly required. The word āyā is a formal marker that clearly announces a yes/no question is coming. In everyday spoken Farsi, people usually drop āyā completely and just raise the pitch of their voice at the end of the sentence, asking in yek sib ast?