يَجِبُ is the central formal-MSA expression of strong obligation: “it is necessary,” “must,” or “has to.” Its ordinary obligation construction is impersonal. Use يجب أن + subjunctive when the responsible person is clear from the subordinate verb, or يجب على + person + أن + subjunctive when the person bearing the duty must be stated explicitly.
English must changes neither for person nor tense, but it sits directly before a bare verb: I must go; they must go. Arabic organizes the clause differently. يجب normally stays third-person masculine singular, while the verb after أن identifies who acts: يجب أن أذهب، يجب أن تذهب، يجب أن يذهبوا.
For the broader modal comparison, see can and must expressions; for a weaker recommendation, compare the dedicated ينبغي reference.
Lookup card: a lexical verb in an impersonal construction
| Item | Verified form | Use |
|---|---|---|
| root and Form | و-ج-ب، Form I | initial-wāw (assimilated) verb |
| perfect | وَجَبَ | became necessary, binding, or due |
| imperfect indicative | يَجِبُ | is necessary; must |
| verbal noun | وُجُوبٌ | necessity, obligatoriness |
| active participle/adjective | وَاجِبٌ | obligatory; duty; required task |
| imperative | — | not used for ordinary obligation; command the required action instead |
| ordinary passive | — | not productive here; وجب is intransitive |
The lexical principal parts are وَجَبَ — يَجِبُ — وُجُوبًا — وَاجِبٌ. The initial و of the root appears in the perfect, maṣdar, and adjective but drops from the imperfect stem: يجب, not يوجب. يُوجِبُ with initial yū- is a different verb, Form IV أوجب / يوجب, meaning “make obligatory, require, entail.”
Calling ordinary obligation يجب “impersonal” does not mean that the root has no other lexical forms. It means that the productive modal construction is conventionally built around singular يجب plus a clause or verbal noun. A learner does not create يجبون to translate “they must.”
يجب أن نراجع الأرقام قبل نشر التقرير.
yajibu ʾan nurājiʿa l-ʾarqāma qabla nashri t-taqrīr.
We must review the figures before publishing the report. (Formal.)
يجب على الزوار إبراز بطاقة هوية عند المدخل.
yajibu ʿalā z-zuwwāri ʾibrāzu biṭāqati huwiyyatin ʿinda l-madkhal.
Visitors must present identification at the entrance. (Formal administrative register.)
يجب أن + subjunctive
Use يجب أن + imperfect subjunctive when the subordinate verb itself makes the actor clear. The ending after أن is visible in careful vocalization: يفعلُ becomes أن يفعلَ. In the forms traditionally called “the five verbs”—imperfects with endings in ـان، ـون، ـين—nūn is deleted: يذهبون becomes أن يذهبوا, and تكتبين becomes أن تكتبي.
يجب أن يصل الطلب قبل الساعة الرابعة.
yajibu ʾan yaṣila ṭ-ṭalabu qabla s-sāʿati r-rābiʿa.
The application must arrive before four o'clock. (Formal.)
يجب أن تتضمن الدراسة بيانات من ثلاث سنوات على الأقل.
yajibu ʾan tataḍammana d-dirāsatu bayānātin min thalāthi sanawātin ʿalā l-ʾaqall.
The study must include data from at least three years. (Academic.)
يجب أن ترسلوا الملاحظات في ملف واحد.
yajibu ʾan tursilū l-mulāḥaẓāti fī malaffin wāḥid.
You must send the comments in one file. (Formal instruction to a male or mixed group; nūn deletion after أن.)
The actor can be a noun inside the subordinate clause: يجب أن يراجع المدير العقد “the director must review the contract.” This is grammatical, but يجب على المدير أن يراجع العقد foregrounds the director as the bearer of the obligation and is often clearer in rules and policies.
يجب على + duty-bearer + أن
Use على to mark the person, group, organization, or authority on whom the obligation rests. The noun after على is genitive. The required action then follows أن and is subjunctive.
يجب على الشركة أن تخطر العملاء بأي تغيير في الأسعار.
yajibu ʿalā sh-sharikati ʾan tukhṭira l-ʿumalāʾa biʾayyi taghyīrin fī l-ʾasʿār.
The company must notify customers of any change in prices. (Formal legal/administrative register.)
يجب عليك أن تحتفظ بالإيصال حتى انتهاء مدة الضمان.
yajibu ʿalayka ʾan taḥtafiẓa bil-ʾīṣāli ḥattā ntihāʾi muddati ḍ-ḍamān.
You must keep the receipt until the warranty period ends. (Formal instruction to one man.)
يجب علينا أن نميز بين الخطأ في البيانات والخطأ في التحليل.
yajibu ʿalaynā ʾan numayyiza bayna l-khaṭaʾi fī l-bayānāti wal-khaṭaʾi fī t-taḥlīl.
We must distinguish between an error in the data and an error in the analysis. (Academic.)
Attached pronouns join على in the usual forms: عليَّ، عليك، عليه، عليها، علينا، عليهم. They do not attach to يجب. Thus “I must” is يجب عليَّ أن..., not a new first-person form of the modal.
A verbal noun instead of an أن-clause
Formal instructions often compress the action into a verbal noun: يجب مراجعةُ العقد “the contract must be reviewed,” يجب على الزوار إبرازُ الهوية “visitors must present identification.” Grammatically, the action noun is what is necessary and therefore behaves as the subject of يجب; in fully marked Arabic it is nominative.
يجب تحديث البيانات كل ستة أشهر.
yajibu taḥdīthu l-bayānāti kulla sittati ʾashhur.
The data must be updated every six months. (Formal administrative register.)
يجب على المورد تسليم المعدات في الموعد المحدد.
yajibu ʿalā l-muwarridi taslīmu l-muʿaddāti fī l-mawʿidi l-muḥaddad.
The supplier must deliver the equipment at the specified time. (Formal contractual register.)
The verbal-noun version is compact and impersonal, which suits regulations. The أن-clause is often easier to process when the action has objects, adverbs, or its own complex structure. Both are standard.
Past obligation: وجب and كان يجب
Lexical perfect وَجَبَ means “became binding, fell due.” It is common in legal, religious, and elevated prose: وجب عليه الدفع “payment became incumbent on him.” For ordinary hindsight—English “should have” or “was supposed to”—كان يجب أن is usually clearer.
وجب على الجهة المتعاقدة رد المبلغ خلال ثلاثين يوما.
wajaba ʿalā l-jihati l-mutaʿāqidati raddu l-mablaghi khilāla thalāthīna yawman.
The contracting party became obliged to return the amount within thirty days. (Formal legal register.)
كان يجب علينا أن نختبر النسخة الاحتياطية قبل الطوارئ.
kāna yajibu ʿalaynā ʾan nakhtabira n-nuskhata l-iḥtiyāṭiyyata qabla ṭ-ṭawāriʾ.
We should have tested the backup before the emergency. (Formal; unmet past obligation.)
An overt lexical subject can trigger ordinary agreement, as in وجبت الصلاة “the prayer became due” (religious). That does not license a personal modal paradigm such as وجبتُ for “I had to.” The ordinary modal keeps the obligation impersonal and marks the obligated person with على.
Negation: must not versus need not
Negation creates a real scope problem. يجب ألا تفعل—with ألا = أن + لا—clearly places negation inside the required action: “you must not do.” لا يجب أن تفعل literally negates necessity and can mean “you need not do,” but contemporary usage sometimes uses it for prohibition too. Avoid that ambiguity in careful writing.
يجب ألا يطلع أي شخص غير مخول على هذه البيانات.
yajibu ʾallā yaṭṭaliʿa ʾayyu shakhsin ghayru mukhawwalin ʿalā hādhihi l-bayānāt.
Unauthorized persons must not view this data. (Formal prohibition: the required state is non-access.)
ليس من الضروري أن تحضر الاجتماع إذا أرسلت ملاحظاتك مسبقا.
laysa mina ḍ-ḍarūriyyi ʾan taḥḍura l-ijtimāʿa ʾidhā ʾarsalta mulāḥaẓātika musbaqan.
You do not need to attend the meeting if you send your comments in advance. (Formal; unambiguous absence of necessity.)
واجب, أوجب, and register
واجب is both an adjective “obligatory” and a noun “duty; assigned task/homework”: إجراء واجب، واجب مهني، الواجب المنزلي. Form IV أوجب / يوجب is transitive “require, make obligatory, entail”: يوجب القانون الإفصاح “the law requires disclosure.” موجب belongs to that Form-IV family; it is not a passive participle of وجب.
يوجب العقد على الطرفين حماية المعلومات السرية.
yūjibu l-ʿaqdu ʿalā ṭ-ṭarafayni ḥimāyata l-maʿlūmāti s-sirriyya.
The contract requires both parties to protect confidential information. (Formal legal register; Form IV أوجب.)
ينبغي usually expresses advisability or expected propriety and is less forceful than legal or procedural يجب. Context can strengthen or weaken either, but a useful production scale is يجب “must” versus ينبغي “should/ought to.”
High-frequency collocations
| Collocation | Meaning and register |
|---|---|
| يَجِبُ أَنْ | it is necessary to / must (neutral formal) |
| يَجِبُ عَلَى شَخْصٍ أَنْ | a person must (formal) |
| يَجِبُ عَلَيْكَ / عَلَيْنَا | you/we must (formal) |
| يَجِبُ أَلَّا | must not (formal, unambiguous) |
| كَانَ يَجِبُ أَنْ | should have / was supposed to (formal) |
| وَاجِبٌ قَانُونِيٌّ | legal duty (formal/legal) |
| وُجُوبُ الِامْتِثَالِ | obligation to comply (legal/academic) |
Common Mistakes
Conjugating يجب personally
❌ يجبون أن يقدموا الطلب اليوم.
Incorrect—the ordinary obligation construction keeps singular impersonal يجب; the plural actor appears in the subordinate verb.
✅ يجب أن يقدموا الطلب اليوم.
yajibu ʾan yuqaddimū ṭ-ṭalaba l-yawm.
They must submit the application today.
Omitting أن before a finite verb
❌ يجب نراجع الشروط مرة أخرى.
Nonstandard in formal MSA—the finite verb requires أن; alternatively use the verbal noun مراجعة.
✅ يجب أن نراجع الشروط مرة أخرى.
yajibu ʾan nurājiʿa sh-shurūṭa marratan ʾukhrā.
We must review the terms again.
Marking the duty-bearer with لـ
❌ يجب للموظف أن يبلغ مديره فورا.
Incorrect for the person bearing the duty—the established obligation frame uses على.
✅ يجب على الموظف أن يبلغ مديره فورا.
yajibu ʿalā l-muwaẓẓafi ʾan yuballigha mudīrahu fawran.
The employee must notify his manager immediately.
Key Takeaways
- The modal construction normally keeps يجب in the third-person masculine singular.
- Use يجب أن + subjunctive for the required action and يجب على + person + أن for the duty-bearer.
- A verbal noun can replace the clause in compact formal rules: يجب تحديث البيانات.
- Use كان يجب أن for an unmet past obligation and يجب ألا for a clear prohibition.
- Keep يجب separate from Form IV يوجب “requires/entails” and from advisory ينبغي “should.”
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Start learning Arabic →Related Topics
- قدر — be ableB1 — Use Form-I قدر for ability with على or أن while separating its older measure/decree senses from Form-II قدّر.
- ينبغي — express formal advisability in a largely fixed imperfect formB2 — Use ينبغي for formal recommendations, choose its أن-clause and beneficiary frames, and express time and negation idiomatically.
- كان — beA2 — Reference the hollow verb كان across its full paradigm, copular and existential senses, predicate case, conditionals, and high-frequency collocations.
- Ability and ObligationA2 — Distinguish personal ability, impersonal possibility, firm obligation, and formal advisability with أستطيع، يمكن، يجب، and ينبغي.
- Advice versus ObligationA2 — Calibrate recommendations and duties in formal MSA with من الأفضل، ينبغي، يجب, and عليك أن while respecting authority and addressee gender.