Expressing General Rules
To state rules like "one must" or "you can't" for people in general (rather than a specific person), Farsi uses impersonal modals combined with the short infinitive. We will explore this while discussing driving regulations.
The Short Infinitive
To form the short infinitive, simply take the full infinitive and drop the final ن.
For example, the full infinitive for "to stop" is:
| to stop | توقف کردنtavaqqof kardan |
Dropping the ن gives the short infinitive: توقف کرد. Similarly, سبقت گرفتن (to overtake) becomes سبقت گرفت.
"One Must" (باید)
To express a general obligation ("one must"), use the invariant modal باید. Because it applies to anyone, the verb takes no personal endings, appearing as the short infinitive at the end of the sentence.
| In the street, one must pay attention to the signs. | در خیابان باید به تابلوها توجه کرد.dar khiyâbân bâyad be tâblohâ tavajjoh kard. |
| One must always put both hands on the steering wheel. | همیشه باید هر دو دست را روی فرمان گذاشت.hamishe bâyad har do dast râ ruye farmân gozâsht. |
| For the exam, one must give the driver's license to the officer. | برای امتحان باید گواهینامه را به افسر داد.barâye emtehân bâyad gavâhinâme râ be afsar dâd. |
"One Can" / "One Cannot" (میتوان / نمیتوان)
To talk about general permission ("one can"), use the impersonal modal میتوان with the short infinitive. To make it negative ("one cannot"), add the negative prefix نـ to get نمیتوان.
| Here one can stop, but one cannot overtake. | اینجا میتوان توقف کرد ولی نمیتوان سبقت گرفت.injâ mitavân tavaqqof kard vali nemitavân sabqat gereft. |
| Without a driver's license, one cannot drive. | بدون گواهینامه نمیتوان رانندگی کرد.bedun-e gavâhinâme nemitavân rânandegi kard. |
| At high speed, one cannot overtake other cars. | با سرعت زیاد نمیتوان از ماشینهای دیگر سبقت گرفت.bâ sor'at ziyâd nemitavân az mâshin-hâye digar sabqat gereft. |
These structures are perfect for discussing rules, instructions, and advice.
| In bad weather, one must brake slowly and be careful. | در هوای بد باید آرام ترمز گرفت و مواظب بود.dar havâ-ye bad bâyad ârâm tormoz gereft o movâzeb bud. |