Exception removes what follows the particle from the ruling before it. The particles are illā, ghayr, siwā, khalā, ʿadā, and ḥāshā. After illā the excepted noun is accusative in a complete affirmative sentence, accusative or a substitute in a complete negative one, and takes the case of its role when the sentence is incomplete.
Exception looks simple and turns out to be one of the most decision-heavy chapters in the grammar. The case of the excepted noun does not depend on the word itself but on what came before the instrument: whether the whole was mentioned, and whether the sentence was affirmative or negative. Three configurations, three different answers, and one of them is the sentence a Muslim says most often.
An exception has three parts: the whole, the instrument, and the excepted. The instruments are illā, the nouns ghayr and siwā, and ʿadā, khalā and ḥāshā, which hover between verb and preposition.
By the end of this lesson
Sort the instruments by what they are, because that decides how they are parsed.
Look at what precedes illā. Complete and affirmative means the accusative is obligatory. Complete and negative means substitution is preferred and the accusative is permitted. Emptied means you parse by role.
قَامَ الْقَوْمُ إِلَّا زَيْدًا
qāma l-qawmu illā Zaydan
The people stood, except Zayd.
قام فعل ماضٍ مبني على الفتح، القومُ فاعل مرفوع وعلامة رفعه الضمة الظاهرة، إلا أداة استثناء، زيدًا مستثنى بإلا منصوب وعلامة نصبه الفتحة الظاهرة.
مَا قَامَ الْقَوْمُ إِلَّا زَيْدٌ
mā qāma l-qawmu illā Zaydun
The people did not stand, except Zayd.
ما حرف نفي، قام فعل ماضٍ مبني على الفتح، القومُ فاعل مرفوع، إلا أداة استثناء، زيدٌ بدل من القوم مرفوع وعلامة رفعه الضمة الظاهرة، ويجوز نصبه على الاستثناء.
Two readings are permitted here and both are correct Arabic. Substitution, badal, is preferred: Zayd takes the case of the whole he is substituted for. The accusative on exception is also allowed.
مَا جَاءَ إِلَّا زَيْدٌ
mā jāʾa illā Zaydun
No one came except Zayd.
ما حرف نفي، جاء فعل ماضٍ مبني على الفتح، إلا أداة حصر، زيدٌ فاعل مرفوع وعلامة رفعه الضمة الظاهرة.
No whole was mentioned, so the sentence is emptied and illā governs nothing at all. Zaydun is simply the doer of jāʾa. Putting it in the accusative here is the commonest error in the chapter: there is nothing to except it from.
Check yourself
What case does the noun after illā take, and why?
مَا رَأَيْتُ إِلَّا مُحَمَّدًا
Accusative, but as a direct object, not as an excepted noun.
The sentence is emptied: no whole precedes illā. So Muḥammadan takes the case its own role requires, and its role is the object of raʾaytu. The accusative here is a coincidence of role, not of exception.
These are nouns. Each takes the case the excepted noun would have taken after illā, and what follows is genitive by annexation.
قَامَ الْقَوْمُ غَيْرَ زَيْدٍ
qāma l-qawmu ghayra Zaydin
The people stood, except Zayd.
قام فعل ماضٍ مبني على الفتح، القومُ فاعل مرفوع، غيرَ مستثنى منصوب وعلامة نصبه الفتحة الظاهرة وهو مضاف، زيدٍ مضاف إليه مجرور وعلامة جره الكسرة الظاهرة.
Compare card 1 above. The case that sat on Zaydan there now sits on ghayra, and Zayd has become genitive by annexation. ghayr absorbs the ruling and passes the genitive on.
Two readings are open: as past verbs putting what follows in the accusative, or as prepositions putting it in the genitive. If mā precedes, only the verbal reading remains.
قَامَ الْقَوْمُ مَا خَلَا زَيْدًا
qāma l-qawmu mā khalā Zaydan
The people stood, apart from Zayd.
قام فعل ماضٍ مبني على الفتح، القومُ فاعل مرفوع، ما مصدرية، خلا فعل ماضٍ مبني على الفتح، والفاعل ضمير مستتر، زيدًا مفعول به منصوب وعلامة نصبه الفتحة الظاهرة.
Without mā, both khalā Zaydan and khalā Zaydin would be correct. With mā the word must be a verb, because mā here is the infinitival mā and only a verb can follow it, so the accusative is required.
lā ilāha illā Llāh combines two chapters, exception and the lā of absolute negation, which is why it repays parsing carefully.
لَا إِلَٰهَ إِلَّا اللهُ
lā ilāha illā Llāhu
There is no god except Allah.
لا نافية للجنس، إلهَ اسم لا مبني على الفتح في محل نصب، وخبر لا محذوف وجوبًا تقديره موجودٌ أو حقٌّ، إلا أداة استثناء، لفظ الجلالة بدل من محل اسم لا مرفوع وعلامة رفعه الضمة الظاهرة.
Note what is happening. ilāha is built on fatḥa, not accusative by fatḥa, because the noun of this lā is built. Its predicate is obligatorily omitted. And lafẓ al-jalāla is nominative because it substitutes for the position of ilāha, which as a subject-like element would be nominative. Reading Allāhu as an excepted noun would require the accusative, which is not what the phrase says.
The configurations and the treatment of each instrument follow these texts.
A rule is clearest in a text you already know by heart. Each ayah below contains the very construction this lesson teaches, and every one has a full word-by-word i'rab on this site. Read the ayah first and try to find the construction yourself, then open its i'rab to check.
Common questions
Three: the mustathnā minhu, the whole from which something is excepted; the instrument, such as illā; and the mustathnā, the thing excepted. In qāma l-qawmu illā Zaydan, al-qawmu is the whole, illā the instrument, and Zaydan the excepted.
Complete, tāmm, means the whole is mentioned before the instrument. Emptied, mufragh, means it is not, so the sentence is empty of it and whatever follows illā takes the case its own role requires. mā jāʾa illā Zaydun is emptied: Zaydun is simply the doer of jāʾa.
They are nouns, not particles. Each takes the case that the excepted noun would have taken after illā, and what follows them is genitive by annexation. So qāma l-qawmu ghayra Zaydin has ghayra accusative and Zaydin genitive.
Two readings are permitted. Treated as past verbs, they put what follows in the accusative as an object; treated as prepositions, they put it in the genitive. Both are correct. But if mā precedes, they must be verbs and the accusative is required.
Because the sentence is emptied: no whole was mentioned before illā, so illā governs nothing and the noun takes the case its own role in the sentence requires. Here it is the doer of jāʾa, so it is nominative.
lā is the lā of absolute negation, ilāha is its noun, built on fatḥa in the position of accusative, its predicate is omitted and estimated as mawjūdun or ḥaqqun, and lafẓ al-jalāla is a substitute (badal) for the position of ilāha, therefore nominative. This is the analysis most commonly taught.