Learn Farsi: یادم رفت که کپی سند باید پیوست بشود. - I forgot that the copy of the document must be attached.

The current lesson teaches that the passive is formed with a past participle plus a form of شدن. Why does this sentence use پیوست بشود without the usual 'eh' participle ending?

While simple verbs form the passive with a full past participle (like نوشته بشود), this sentence uses the compound verb پیوست کردن (to attach). In passive compound verbs, the non-verbal part (پیوست) stays exactly the same, and only the auxiliary verb changes to the passive subjunctive بشود.

What is forcing the verb بشود into the present subjunctive form?

The modal word باید (must) requires the verb that follows it to be in the present subjunctive. Even though the first part of the sentence is in the past tense (یادم رفت), the action of attaching the document is a requirement, so باید triggers the subjunctive بشود.

Why does یادم رفت translate to 'I forgot' when the verb رفت means 'went' and is in the third-person singular?

This is a very common Farsi idiom that translates literally to 'my memory went.' The grammatical subject of the phrase is the noun یاد (memory), which is why the verb رفت is in the third-person singular. The م suffix on یاد shows that it is your memory!

Is there a hidden sound between the words کپی and سند?

Yes, there is an unseen ezafe linking the two nouns to mean 'copy of the document.' Because ends in a long vowel sound, the ezafe is pronounced with a 'ye' sound to smoothly bridge the words, making it sound like 'kopi-ye sanad'.