Learn Farsi: برای این پیراهن باید یا از ابریشم استفاده کنید یا از پنبه. - You must use either silk or cotton for this shirt.

When using correlative conjunctions like یا... یا... (either... or...) with a verb that requires a preposition, Farsi speakers usually repeat the preposition before each option. Since استفاده کردن (to use) takes the preposition از, it feels most natural and balanced to say یا از ابریشم... یا از پنبه.

Why is the verb استفاده کنید placed before the second یا, instead of at the very end of the sentence?

While Farsi normally places verbs at the end, structures like یا... یا... often bend this rule. You certainly could put both options together before the verb (...یا از ابریشم یا از پنبه استفاده کنید), but placing the verb right after the first option is very common and gives clear, balanced emphasis to the two choices.

Because of باید (must), shouldn't the verb have a بـ prefix to show the subjunctive mood, like استفاده بکنید?

Yes, باید triggers the subjunctive mood. However, with compound verbs like استفاده کردن, adding the بـ (be-) prefix to the doing-verb (کردن) is optional. Dropping the prefix to just say استفاده کنید is extremely common and perfectly correct in everyday Farsi.

Why do we need the word از (from) in this sentence when the English translation just says 'use silk'?

The compound verb translates to 'to use', but it literally means 'to make use'. In Farsi, you cannot use an object directly without a preposition; you have to make use 'from' it. Therefore, this verb must always be paired with the preposition .