Learn Farsi: ده سال طول می‌کشد تا این طرح محو شود. - It takes ten years for this design to fade.

tul means "length" or "duration", and the verb keshidan means "to pull" or "to draw". Together, tul keshidan literally means "to pull length". Farsi uses this compound verb to express how much time a process takes to complete.

Why is tâ used here, and why does it trigger the subjunctive?

In English we say "it takes [time] FOR [something to happen]", but Farsi literally says "it takes [time] UNTIL [something happens]". The word tâ acts as "until" here. Because tâ introduces a potential future outcome rather than an established fact, the verb that follows it (mahv shavad) must take the present subjunctive form.

Why doesn't the subjunctive verb mahv shavad have the usual be- prefix?

mahv shodan is a compound verb meaning "to fade" or "to disappear", using the helper verb shodan (to become). While the subjunctive of shodan can be beshavad, modern Farsi almost always drops the be- prefix for shodan when it is part of a compound verb. So it simply becomes shavad.

Why is sâl (year) in the singular form when the English translation says "ten years"?

This is a very important rule in Farsi: anytime you use a specific number before a noun, the noun must stay in its singular form. You will never use a plural marker after a number, which is why "ten years" is always just .