Learn Farsi: من شک دارم که آنها یک سیستم فاضلاب در ون خودشان داشته باشند. - I doubt that they have a wastewater system in their own van.

The verb dâshtan (to have) does not form its present subjunctive the regular way with a be- prefix. Instead, it uses its past participle dâshte combined with the subjunctive forms of 'to be'. Since the subject is 'they', it uses the third-person plural form bâshand.

The sentence uses both dâram and dâshte bâshand. Why isn't dâram also in the subjunctive?

The first clause man shakk dâram (I doubt) is a factual statement about your current state of mind, so it uses the standard present indicative. The second clause is the thing you are uncertain about, which is why the phrase shakk dâram ke triggers the subjunctive mood only for the second verb.

How does khodeshân work to mean 'their own' in this context?

The word khod means 'self'. By adding the plural third-person possessive suffix -eshân (their), it literally means 'their selves'. When placed after a noun in an ezafe chain, like van-e khodeshân, it translates naturally as 'their own van' and adds emphasis to the possession.

How is the compound word fâzelâb (wastewater) formed?

It is formed by combining fâzel (an Arabic-origin word meaning surplus or waste) and âb (the Persian word for water). Joining these together creates the standard Farsi term for sewage or wastewater.