In short

Every Arabic noun and every imperfect verb carries a small ending that announces its job in the sentence. الْمُدَرِّسُ with a ḍamma is the one doing something; الْمُدَرِّسَ with a fatḥa is the one something is done to; الْمُدَرِّسِ with a kasra sits after a preposition or after a possessed noun. You have been meeting these endings one at a time since lesson 2 - a مُبْتَدَأ here, a مَفْعول بِهِ there. This lesson puts the whole system on one page and names it: الإِعْرابُ.

Two things make it more than a table of three vowels. First, a handful of word classes refuse those vowels and use a letter instead - a و، ا، ي or a ن you can hear across a room, or in one famous case a kasra where you expected a fatḥa. Those substitutes are الْعَلاماتُ الْفَرْعِيَّةُ, and they are where learners lose marks. Second, the imperfect verb plays the same game with a fourth state of its own, الْجَزْم. Learn to read all of it here; how much of it you will ever hear is the last thing this lesson tells you.

The rule

1. What إِعْراب actually is. A word’s ending is not chosen by the word. It is imposed by whatever governs it - the sentence position, the preceding particle, the preceding verb. Arabic calls the four resulting states الرَّفْعُ، النَّصْبُ، الجَرُّ، الجَزْمُ, and calls the vowel or letter that shows the state الْعَلامَة, “the marker”. Nouns take the first three and never the fourth; imperfect verbs take the first, the second and the fourth, and never الجَرّ. One line holds the division in place: الجَرُّ لِلْأَسْماءِ والجَزْمُ لِلْأَفْعالِ.

The English names work as labels - مَرْفوع = nominative, مَنْصوب = accusative, مَجْرور = genitive, مَجْزوم = jussive - but as labels only: Arabic’s مَنْصوب covers the direct object, the adverbial, the خَبَر of كانَ and much else besides.

2. The default markers, on an ordinary singular noun. For the great majority of nouns the marker is the vowel you expect: ḍamma for الرَّفْع, fatḥa for النَّصْب, kasra for الجَرّ. Indefinite, that vowel is doubled into tanwīn - مُدَرِّسٌ، مُدَرِّسًا، مُدَرِّسٍ. Barred from tanwīn, whether by الـ or by being the first term of an إِضافَة, it collapses to a single vowel - الْمُدَرِّسُ، الْمُدَرِّسَ، الْمُدَرِّسِ and مُدَرِّسُ الْمَدْرَسَةِ. Tanwīn can share a word neither with الـ nor with a following مُضاف إِلَيْهِ.

3. What puts a noun in each state. Each item on this short list is a lesson you already have. مَرْفوع: المُبْتَدَأ and الخَبَر (lesson 2), and الفاعِل, the doer of a verb (lesson 19). مَنْصوب: المَفْعولُ بِهِ (lesson 29), the adverbial of time or place (lesson 31), خَبَرُ كانَ (lesson 32). مَجْرور: after any حَرْف جَرّ (lesson 16), and as the second term of an إِضافَة (lesson 20).

4. Writing the accusative: the alif that is spelling, not sound. Indefinite النَّصْب adds a written alif after the noun: كِتابٌ → كِتابًا، بَيْتٌ → بَيْتًا، دَرْسٌ → دَرْسًا. Print the fatḥatān over the letter before that alif. It has no sound of its own in connected speech; it is there so the eye can see the accusative in an unvocalized text - and, as point 10 explains, it is what you hear when the speaker stops.

Two classes of word take no alif here (a third, the اسْم مَقْصور, is lesson 41). A noun ending in ة simply switches the tanwīn: مَدْرَسَةٌ → مَدْرَسَةً، سَيّارَةٌ → سَيّارَةً. Nor does a noun ending in ء that already sits on a long ā: سَماءٌ → سَماءً، ماءٌ → ماءً، مَساءٌ → مَساءً. Where the hamza is not preceded by that alif, the written alif comes back: شَيْءٌ → شَيْئًا.

5. الْعَلاماتُ الْفَرْعِيَّةُ: four classes that use something else. These are the exceptions worth memorising, because they are visible and audible where ordinary endings are neither.

• الأَسْماءُ الخَمْسَةُ - five nouns (أَب، أَخ، حَم، فو، ذو) which, when they are singular and the first term of an إِضافَة to anything but ـي, show their case with a long vowel letter: و for الرَّفْع، ا for النَّصْب، ي for الجَرّ. جاءَ أَبو الطّالِبِ - رَأَيْتُ أَبا الطّالِبِ
  • سَلَّمْتُ عَلى أَبي الطّالِبِ. Standing alone they are perfectly ordinary: أَبٌ، أَبًا، أَبٍ, and with “my” they freeze - أَبي is “my father” in all three cases. In modern prose you will really only meet أَب، أَخ and ذو.
• المُثَنّى - the dual (lesson 12) has two forms for three cases: ـانِ for الرَّفْع، ـيْنِ for both النَّصْب and الجَرّ. الطّالِبانِ نَجَحا - رَأَيْتُ الطّالِبَيْنِ - مَعَ الطّالِبَيْنِ. The ن of the dual always carries a kasra.
• جَمْعُ المُذَكَّرِ السّالِمُ - the sound masculine plural (lesson 9) does the same with ـونَ and ـينَ, and here the ن always carries a fatḥa: الْمُدَرِّسونَ حاضِرونَ - سَأَلْتُ الْمُدَرِّسينَ.
• جَمْعُ المُؤَنَّثِ السّالِمُ - the sound feminine plural keeps a vowel but borrows the wrong one: its accusative takes a kasra, never a fatḥa. الْمُعَلِّماتُ حاضِراتٌ - رَأَيْتُ الْمُعَلِّماتِ - مَعَ الْمُعَلِّماتِ. Indefinite, the same: رَأَيْتُ مُعَلِّماتٍ, kasratān and no alif. This is the most-corrected error at B1: the ear wants a fatḥa on an object, and this ending refuses to give one.

6. The verb’s three states. Of the verbs, only the imperfect, المُضارِع, is مُعْرَب - and even it freezes in the two cells that end in نون النِّسْوَة (point 7). Its default is المَرْفوع, with a ḍamma - يَكْتُبُ. A subjunctive particle (lesson 33) swaps that for a fatḥa - لَنْ يَكْتُبَ. A jussive particle (lesson 35) swaps it for a sukūn - لَمْ يَكْتُبْ. So الجَزْم is simply “no vowel at all”, the fourth state and the one nouns never see.

7. The verb’s own فَرْعِيّ markers: two deletions. Where a verb cannot show a vowel, it shows the state by dropping something.

• حَذْفُ النّونِ. الأَفْعالُ الخَمْسَةُ - the five cells ending in ن (تَكْتُبينَ، تَكْتُبانِ، يَكْتُبانِ، تَكْتُبونَ، يَكْتُبونَ) - are مَرْفوع with that ن and lose it in both المَنْصوب and المَجْزوم: يَكْتُبونَ → لَنْ يَكْتُبوا، لَمْ يَكْتُبوا. The silent alif after ـوا is compulsory spelling.
• حَذْفُ حَرْفِ الْعِلَّةِ. A verb whose last letter is و، ا or ي (lesson 51) has nowhere to put a sukūn, so المَجْزوم amputates that letter: يَمْشي → لَمْ يَمْشِ، يَدْعو → لَمْ يَدْعُ، يَنْسى → لَمْ يَنْسَ. The short vowel left behind is the trace of the missing letter, and the whole visible difference between “he walks” and “he did not walk”.

And two cells move for nobody: يَكْتُبْنَ and تَكْتُبْنَ are مَبْنِيّ, identical in all three states, because their ن is the subject pronoun and not a marker.

8. المَبْنِيُّ: the words that never change. A large part of the language is exempt. مَبْنِيّ means “built, fixed” - one shape, kept whatever the word’s job. The main groups: the pronouns (أَنا، هُوَ، هُمْ، and the attached ـهُ، ـكَ، ـي), the demonstratives (هٰذا، هٰذِهِ، ذٰلِكَ، أُولٰئِكَ), the relatives (الَّذي، الَّتي، الَّذينَ), the past tense (كَتَبَ، كَتَبْتُ، كَتَبوا), the imperative (اُكْتُبْ، اِجْلِسْ), and most question words (مَنْ، ما، كَيْفَ، مَتى). The duals are the exception inside the exception: هٰذانِ / هٰذَيْنِ and اللَّذانِ / اللَّذَيْنِ do inflect, exactly like المُثَنّى.

9. مَحَلُّ الإِعْرابِ, in one paragraph. A مَبْنِيّ word still has a job, so grammarians say it is in the position of a case: فِي مَحَلِّ رَفْعٍ، فِي مَحَلِّ نَصْبٍ، فِي مَحَلِّ جَرٍّ. In قَرَأْتُ هٰذا الْكِتابَ the object is هٰذا - frozen in shape, but فِي مَحَلِّ نَصْبٍ, with the following الْكِتابَ showing the fatḥa on its behalf. In بَيْتُهُ the ـهُ is فِي مَحَلِّ جَرٍّ, and whole clauses get the same treatment. You never have to produce this vocabulary, but it explains why an Arabic grammar will call a word “accusative” when it visibly has no fatḥa on it.

10. Almost none of this is audible. In الْوَقْف - stopping at the end of a phrase - Arabic drops the final short vowel and the tanwīn, as the pronunciation guide sets out. الْمُدَرِّسُ، الْمُدَرِّسَ and الْمُدَرِّسِ are all pronounced الْمُدَرِّسْ; لَنْ يَكْتُبَ and لَمْ يَكْتُبْ come out the same. The one survivor is the indefinite accusative, whose alif is read as a long ā: رَأَيْتُ كِتابًا ends in -ā. So the vowel markers are heard only where nothing is dropped - careful reading aloud, a newsreader’s delivery, formal speeches, recitation - and inside a phrase that runs on.

The letter markers are a different story. ـونَ against ـينَ، ـانِ against ـيْنِ، أَبو against أَبا against أَبي، and a missing ن are consonantal: they cannot be dropped, and they are heard whenever anyone speaks فُصْحى at all. Hence the practical rank order of this lesson - the فَرْعِيّ markers you need for speech, the أَصْلِيّ ones for writing and reading aloud.

11. Left to the next lesson. المَمْنوعُ مِنَ الصَّرْفِ refuses tanwīn and takes a fatḥa instead of a kasra in الجَرّ, and الاسْمُ المَقْصورُ (مُسْتَشْفى) and المَنْقوصُ (القاضي) hide their endings inside a final long vowel. All of that is lesson 41.

Forms & patterns

The four states and their default markers:

An ordinary indefinite noun:

The same noun made definite - one vowel instead of tanwīn:

الْعَلاماتُ الْفَرْعِيَّةُ, all four classes in one grid:

The written alif of the indefinite accusative:

The imperfect verb across its three states - the sound verb first, then the cells that drop a ن, then the weak-final verbs that drop a letter. The duals of the weak verbs are left out; they behave like the plurals.

Words that sit outside the system altogether:

Examples

Common mistakes

• رَأَيْتُ الْمُعَلِّماتَ -> رَأَيْتُ الْمُعَلِّماتِ - the sound feminine plural has no fatḥa at all. Its accusative borrows the genitive’s kasra, and looks identical to it.
• سَأَلْتُ الْمُدَرِّسونَ -> سَأَلْتُ الْمُدَرِّسينَ - ـونَ marks الرَّفْع only. An object, and anything after a preposition, takes ـينَ.
• مَعَ الطّالِبانِ -> مَعَ الطّالِبَيْنِ - the dual works the same way: ـانِ for the subject, ـيْنِ everywhere else, with a kasra on the ن.
• رَأَيْتُ أَبو الطّالِبِ -> رَأَيْتُ أَبا الطّالِبِ - one of الأَسْماء الخَمْسَة, so its accusative is the letter ا, not a fatḥa on a ب.
• قَرَأْتُ كِتابٍ -> قَرَأْتُ كِتابًا - a direct object is مَنْصوب. The kasratān belongs after a preposition or in an إِضافَة, not after a transitive verb.
• زُرْنا مَدْرَسَةاً -> زُرْنا مَدْرَسَةً - a noun ending in ة takes no written alif, and neither does سَماءً after its long ā. Adding one is a spelling error, not a variant.
• لَمْ يَكْتُبُ -> لَمْ يَكْتُبْ - لَمْ demands الجَزْم, and the marker of الجَزْم is the absence of a vowel.
• لَمْ يَكْتُبونَ -> لَمْ يَكْتُبوا - one of الأَفْعال الخَمْسَة: الجَزْم removes the ن, and the silent alif is written in its place.
• لَمْ يَمْشي -> لَمْ يَمْشِ - a weak-final verb marks الجَزْم by deleting its last letter, leaving only the kasra that used to support it.
• كَتَبُ الطّالِبُ الدَّرْسَ -> كَتَبَ الطّالِبُ الدَّرْسَ - the past tense is مَبْنِيّ. Its fatḥa is fixed and has nothing to do with case; it never turns into a ḍamma.

Tips

• Learn the system as two lists, not one: the three plain vowels for ordinary nouns, and the four فَرْعِيّ classes. Almost every ending you will ever write is in one list or the other.
• Drill the four فَرْعِيّ classes out loud in triplets - أَبو أَبا أَبي، الطّالِبانِ الطّالِبَيْنِ الطّالِبَيْنِ، الْمُدَرِّسونَ الْمُدَرِّسينَ الْمُدَرِّسينَ. They are consonants, so they survive into real speech and repay the effort immediately.
• Keep one sentence permanently in your head as the antidote to the commonest error in this lesson: رَأَيْتُ الْمُعَلِّماتِ. Kasra on an object, and it is correct.
• Use the memory line الجَرُّ لِلْأَسْماءِ والجَزْمُ لِلْأَفْعالِ whenever you are unsure which of the four states a word can even be in.
• Do not hunt for case endings in an ordinary unvocalized newspaper - they are not printed. Look instead for what is spelled: the alif of ـًا, the ـونَ / ـينَ pair, a missing ن.
• Practise by reading a vocalized text aloud without stopping between words. Running the phrase on is the only situation that forces you to pronounce these endings.
• Ignore, for now, formal إِعْراب parsing - the exercise where you label every word مَرْفوعٌ وعَلامَةُ رَفْعِهِ كَذا. It is a school tradition, not a route to fluency.