Persian speakers can temporarily admit a proposition for the sake of reasoning without claiming that it is true. فرض کنیم نرخ تورم ثابت بماند means “Let us suppose the inflation rate remains constant”: speaker and audience place the proposition on the table, then examine what follows. به فرض اینکه این تفسیر درست باشد “assuming that this interpretation is correct” creates greater distance and often introduces a concession.
These frames are central to (academic) argument, policy discussion, proofs, and careful disagreement. They also have conversational counterparts such as فرض کن “suppose/imagine.” Their usual subjunctive expresses an entertained scenario rather than an established fact.
The main frames
| Frame | Function | Typical register |
|---|---|---|
| فرض کنیم (که) P | jointly introduce P as a working hypothesis | neutral/formal, academic |
| فرض کنید (که) P | ask the audience to imagine P | formal/polite instruction |
| فرض کن (که) P | ask one familiar addressee to imagine P | informal/neutral conversation |
| به فرض اینکه P | grant P provisionally, often before a reservation | formal/academic |
| فرض بر این است که P | state the maintained assumption of a model or procedure | formal/academic |
فرض کنیم نرخ تورم ثابت بماند؛ در این صورت قدرت خرید خانوار چه تغییری میکند؟
farz konim nerkh-e tavarrom sâbet be-mânad; dar in surat qodrat-e kharid-e khânevâr che taghyiri mi-konad?
Let us suppose the inflation rate remains constant; in that case, how does household purchasing power change? (academic)
به فرض اینکه این تفسیر درست باشد، هنوز دو شاهد با آن سازگار نیست.
be farz-e in-ke in tafsir dorost bâshad, hanuz do shâhed bâ ân sâzgâr nist.
Even assuming this interpretation is correct, two pieces of evidence are still incompatible with it. (academic; provisional concession)
English suppose, assuming that, and granted that likewise manage an argument, but English does not visibly mark the embedded verb for mood. Persian usually does: بماند، باشد، وجود داشته باشد present the proposition as hypothetical, not as the speaker's factual commitment.
فرض کنیم: building a shared model
فرض کنیم is formally first-person plural—literally “let us suppose”—and its inclusive force makes reasoning collaborative. که may follow it, especially before a long clause, but is often omitted before a short, tightly integrated hypothesis. The choice does not change the truth conditions.
فرض کنیم که همهی شرکتکنندگان به پرسش نخست درست پاسخ بدهند.
farz konim ke hame-ye sherkat-konandegân be porsesh-e nokhost dorost pâsokh be-dahand.
Let us suppose that all participants answer the first question correctly. (academic; explicit که before a longer clause)
فرض کنیم قطار ده دقیقه دیرتر برسد؛ زمان کافی برای عوض کردن خط داریم.
farz konim qatâr dah daqiqe dir-tar be-rasad; zamân-e kâfi barâ-ye avaz kardan-e khat dârim.
Suppose the train arrives ten minutes late; we have enough time to change lines. (neutral practical reasoning)
The continuation commonly begins with در این صورت “in that case,” آنگاه “then” (formal), or a direct question. This creates an explicit reasoning chain: hypothesis first, consequence or test second. See Building Conditional Arguments for longer structures.
Addressing one person or an audience
Change کنیم only when the speech act changes. فرض کن invites one familiar person into a scenario; فرض کنید addresses several people or one person politely. The embedded hypothetical clause still normally has its own subjunctive.
فرض کن کیف پولت را در تاکسی جا بگذاری؛ اول به چه کسی زنگ میزنی؟
farz kon keyf-e pul-at râ dar tâksi jâ be-gozâri; avval be che kasi zang mi-zani?
Suppose you leave your wallet in a taxi; who do you call first? (neutral conversation)
برای لحظهای فرض کنید هیچ محدودیت بودجهای وجود نداشته باشد.
barâ-ye lahze-i farz konid hich mahdudiyyat-e budje-i vojud na-dâshte bâshad.
For a moment, suppose there were no budget constraint. (formal presentation or classroom instruction)
This imperative use is not rude by itself, but فرض بفرمایید is possible in very deferential speech and sounds conspicuously (formal/honorific). It is not necessary in ordinary teaching.
به فرض اینکه and speaker distance
به فرض اینکه packages the assumption as a background condition. It often means “even granting that,” especially with باز هم “even so/still” in the main clause. The speaker may regard P as doubtful, but the construction itself does not encode disbelief; context supplies that stance.
به فرض اینکه وام امروز تصویب شود، پرداخت آن دستکم یک ماه طول میکشد.
be farz-e in-ke vâm emruz tasvib shavad, pardâkht-e ân dast-kam yek mâh tul mi-keshad.
Assuming the loan is approved today, its disbursement will take at least a month. (formal administrative)
به فرض اینکه آمار کامل باشد، باز هم از همبستگی نمیتوان علیت را نتیجه گرفت.
be farz-e in-ke âmâr kâmel bâshad, bâz ham az ham-bastegi nemi-tavân elliyyat râ natije gereft.
Even assuming the data are complete, one still cannot infer causation from correlation. (academic; concessive supposition)
The shorter به فرضِ P can take a noun phrase: به فرضِ موفقیت طرح “assuming the plan's success.” With a finite clause, به فرض اینکه is the transparent modern choice. به فرض آنکه is a more elevated (formal/literary) variant.
A maintained assumption: فرض بر این است که
An analyst may move from the act of supposing to a standing assumption: فرض بر این است که ... “the assumption is that ...”. Here the complement reports the content of an adopted model, so an indicative—including a perfect—can be appropriate. This does not contradict the subjunctive tendency after فرض کنیم; the two predicates perform different discourse jobs.
در این مدل، فرض بر این است که پاسخدهندگان دستورالعمل را با دقت خواندهاند.
dar in model, farz bar in ast ke pâsokh-dahandegân dastur-ol-amal râ bâ deqqat khânde-and.
In this model, the assumption is that respondents have read the instructions carefully. (academic; stated model assumption)
Do not mechanically force every clause containing the noun فرض into the subjunctive. Mood follows the clause's status: newly entertained possibility favors the subjunctive; a report of the model's already defined contents may use the indicative.
Common Mistakes
1. Using an infinitive for an open supposition
❌ فرض کنیم قیمت ثابت ماندن.
Incorrect — the hypothesis needs a finite subjunctive, not infinitive ماندن.
✅ فرض کنیم قیمت ثابت بماند.
farz konim qeymat sâbet be-mânad.
Let us suppose the price remains constant. (academic)
2. Stacking two complementizers
❌ به فرض که اینکه جلسه لغو شود، چه میکنیم؟
Incorrect — use one finite-clause frame, normally به فرض اینکه.
✅ به فرض اینکه جلسه لغو شود، چه میکنیم؟
be farz-e in-ke jalase laghv shavad, che mi-konim?
Assuming the meeting is cancelled, what will we do?
3. Treating a supposition as proof
The sequence فرض کنیم دارو مؤثر باشد، پس ثابت شد که مؤثر است is grammatically interpretable but logically invalid: a provisional assumption cannot by itself establish the same proposition as fact.
✅ فرض کنیم دارو مؤثر باشد؛ سپس پیامدهای این فرض را بررسی کنیم.
farz konim dâru mo'asser bâshad; sepas payâmad-hâ-ye in farz râ barrasi konim.
Let us suppose the medicine is effective; then let us examine the consequences of that assumption. (academic)
4. Mismatching the embedded subject and verb
❌ استاد، فرض کنید که این مقدار صفر باشی.
Incorrect — embedded subject این مقدار is third-person singular and requires باشد, not second-person باشی.
✅ استاد، فرض کنید که این مقدار صفر باشد.
ostâd, farz konid ke in meqdâr sefr bâshad.
Professor, suppose this value is zero. (polite/formal)
Key Takeaways
- فرض کنیم (که) P introduces P as a shared working hypothesis; P normally takes the subjunctive.
- فرض کن/کنید changes who is invited to imagine the scenario, not the hypothetical status of the complement.
- به فرض اینکه is formal and distanced, and often grants a premise before باز هم introduces a reservation.
- A supposition does not assert truth or falsity; it licenses an argument about consequences.
- فرض بر این است که reports a maintained model assumption and can therefore take an indicative complement.
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- As If with انگار and گوییB1 — Compare conversational انگار and literary گویی for appearance and as-if clauses, including evidential distance and indicative–subjunctive choices.
- Present Subjunctive FormationA2 — Form the Persian present subjunctive with بـ, the present stem, and personal endings, including vowel allomorphy, preverbs, compounds, irregulars, and stress.