In short

The imperfect you learned in lesson 14 is not one form but three. The version printed there - أَدْرُسُ، تَدْرُسينَ، يَدْرُسونَ, with a ḍamma or a ن on the end - is only its default dress, المُضارِعُ المَرْفوعُ. Put one of a short list of particles in front of it and the end of the verb changes: أَدْرُسُ becomes لَنْ أَدْرُسَ “I will not study”, يَدْرُسونَ becomes أُريدُ أَنْ يَدْرُسوا “I want them to study”. That second dress is المُضارِعُ المَنْصوبُ, the subjunctive.

There are exactly two changes to learn and one exemption. The ḍamma of the five endingless cells turns into a fatḥa. The five cells that end in a ن - الأَفْعالُ الخَمْسَةُ - drop that ن. And يَدْرُسْنَ / تَدْرُسْنَ, the two feminine plurals, are مَبْنِيٌّ: they are frozen and never move in any mood. That is the whole of the machinery. This lesson builds the form and lists the particles that trigger it; what you actually say with أَنْ - want, must, can - is lesson 34.

The rule

1. Mood is not tense. المَنْصوب does not mean past, future or anything temporal. It is a grammatical mood, a shape the verb takes because of the word standing in front of it, exactly as a noun after مِنْ takes a kasra because of مِنْ. Only the imperfect has moods: three of them, and you now have two - المَرْفوع (lesson 14) and المَنْصوب (here). The third, المَجْزوم, is lesson 35. The past tense has no moods at all; ماضٍ is مَبْنِيٌّ and never changes its ending for a particle.

2. Change one: ـُ becomes ـَ. In the five cells that carry no suffix, the final ḍamma is simply replaced by a fatḥa. أَدْرُسُ → أَدْرُسَ، تَدْرُسُ → تَدْرُسَ، يَدْرُسُ → يَدْرُسَ، نَدْرُسُ → نَدْرُسَ. Nothing else about the word moves - the prefix is untouched, the stem keeps its vowel, the sukūn on the first radical stays. One dot of a vowel at the very back, and that is the entire visible difference.

3. Change two: الأَفْعالُ الخَمْسَةُ lose their nūn. Five cells of the imperfect end in a ن: تَدْرُسينَ (أَنْتِ), تَدْرُسانِ (أَنْتُما and هُما feminine), يَدْرُسانِ (هُما masculine), تَدْرُسونَ (أَنْتُمْ), يَدْرُسونَ (هُمْ). Arabic grammar gives these five a name of their own, الأَفْعالُ الخَمْسَةُ, “the five verbs”, precisely because they behave as a block. In المَنْصوب the ن falls off and the long vowel that was in front of it is all that is left: تَدْرُسي، تَدْرُسا، يَدْرُسا، تَدْرُسوا، يَدْرُسوا. That ن was never part of the pronoun; it was نونُ الرَّفْعِ, a mood marker, and removing it is the same operation as swapping the ḍamma for a fatḥa - just visible from across the room.

4. The silent alif after ـوا. When the ن of ـونَ goes, the word ends in a long ū, and Arabic spelling insists on an otiose alif behind it: يَدْرُسوا، تَدْرُسوا. It is written and never pronounced - the form is said exactly as if the alif were not there. Its job is purely visual, to keep a verb ending ـوا apart from a noun ending in و (compare the plural noun مُدَرِّسو المَدْرَسَةِ, with no alif). Grammarians call it الأَلِفُ الفارِقَةُ, “the distinguishing alif”. Write it every time; a bare يَدْرُسو is a spelling error, not a variant.

5. يَدْرُسْنَ and تَدْرُسْنَ never change. The ـنَ of the feminine plural is not a mood marker at all: it is the subject pronoun, welded to the verb. So these two cells are مَبْنِيَّتانِ - built in place - and they are identical in the indicative, the subjunctive and the jussive. لَنْ يَدْرُسْنَ، أُريدُ أَنْ تَدْرُسْنَ: the form you already know, unchanged. Do not try to make them look “more subjunctive”; there is nothing to do to them.

6. The particles that put the verb into المَنْصوب. They are few, and apart from them - and the jussive particles of lesson 35 - the imperfect stays مَرْفوع. Each one stands immediately before its verb: only the negative لا may come between the two (أَلّا، حَتّى لا - point 8 below), and the subject, if there is one, comes after the verb.

• أَنْ - “to / that”, the workhorse. It links a first verb to a second: أُريدُ أَنْ أَدْرُسَ “I want to study”, يَجِبُ أَنْ تَنامَ “you must sleep”. Note that English uses an infinitive here and Arabic uses a full verb carrying its own person.
• لَنْ - “will not”. It negates the future and nothing else: لَنْ أَذْهَبَ “I will not go”. It replaces سَـ / سَوْفَ rather than joining them.
• كَيْ / لِكَيْ - “in order that, so as to”: نَخْرُجُ مُبَكِّرًا كَيْ نَصِلَ فِي الوَقْتِ. لِكَيْ is simply لِـ + كَيْ; both are current in modern prose and interchangeable here.
• لِـ التَّعْليل - a single prefixed لام meaning “in order to”, the lightest way to say purpose: ذَهَبْتُ لِأَشْتَرِيَ الخُبْزَ “I went to buy the bread”. It is a prefix, written joined to the verb with no space. Traditional analysis says the verb here is منصوب by an أَنْ that is understood but not written; you can simply learn لِـ as a subjunctive trigger.
• حَتّى - “until / so that”, when what follows is still ahead at the point the first verb reaches: دَرَسْتُ حَتّى أَنْجَحَ “I studied so that I would pass”. When حَتّى reports a fact that actually did take place it behaves differently; that split is lesson 38.
• إِذَنْ - “then, in that case”, answering what someone has just said: «سَأَزورُكَ غَدًا.» - «إِذَنْ أَنْتَظِرَكَ فِي البَيْتِ.» It only takes the subjunctive when it opens the reply, refers to future time, and touches its verb directly. It is also spelled إِذًا.

7. Only the second verb changes. In a two-verb sentence the first verb keeps whatever shape it would have on its own - مُضارِع مَرْفوع or ماضٍ - and carries the tense; the particle sits between them and bends only what comes after it. أُريدُ (مرفوع) أَنْ أَدْرُسَ (منصوب). دَرَسْتُ (ماضٍ) حَتّى أَنْجَحَ (منصوب). Learners who put the whole sentence into the subjunctive, or who reach back and change the first verb, are hearing an English “sequence of tenses” that Arabic does not have.

8. أَنْ + لا is written أَلّا. The negative of an أَنْ-clause fuses in writing: أُريدُ أَلّا تَذْهَبَ “I want you not to go”, not أَنْ لا تَذْهَبَ. The verb after it is still منصوب. Keep this as a spelling fact for now; the uses of أَنْ-clauses are lesson 34.

9. Weak-final verbs: sometimes visible, sometimes not. Verbs whose last root letter is و or ي (الفِعْلُ النّاقِصُ) already end in a long vowel in the indicative, where the ḍamma is only theoretical - يَمْشي، يَدْعو، يَنْسى are all pronounced with no audible ending. In المَنْصوب two of the three types wake up: يَمْشي → يَمْشِيَ and يَدْعو → يَدْعُوَ put a real, pronounced fatḥa on the final letter. The third does not: a verb ending in ألف مقصورة, like يَنْسى, has no room for a vowel on that ا, so يَنْسى stays يَنْسى - the mood is genuinely there and genuinely invisible. Their plurals behave like everyone else’s and drop the ن: يَمْشُونَ → يَمْشُوا، يَدْعُونَ → يَدْعُوا، يَنْسَوْنَ → يَنْسَوْا. The full story of these verbs is lesson 51.

10. In الوَقْف the mood disappears. A speaker who stops at the end of a phrase drops the final short vowel, as the pausal form requires, so يَدْرُسُ and يَدْرُسَ are pronounced identically - both come out as يَدْرُسْ. The fatḥa of the subjunctive is therefore audible only in careful reading, in recitation, in a newsreader’s delivery, and whenever the verb is not the last word of the phrase. What is always audible, in every register of الفُصْحى including the most relaxed, is the missing ن: تَدْرُسوا and تَدْرُسونَ can never be confused. This is why الأَفْعالُ الخَمْسَةُ are the part of the lesson that pays for itself immediately, and why المَنْصوب is a live rule and not a decoration for textbooks.

11. What is deliberately not here. What أَنْ-clauses are for - want, must, can, and the frames built on them - is lesson 34. Choosing between لَنْ، ما and لَمْ is lesson 37. Full time-and-reason clauses with حَتّى، قَبْلَ أَنْ، بَعْدَ أَنْ are lesson 38. The lookalike particle أَنَّ, which takes a noun in the accusative and is a different word entirely, is lesson 44. And the fact that أَنْ + verb can be swapped for a verbal noun - أُريدُ الذَّهابَ for أُريدُ أَنْ أَذْهَبَ - is lesson 54.

Forms & patterns

The two moods side by side, all thirteen cells, on the sound Form I verb دَرَسَ - يَدْرُسُ. Read down the middle and right columns together: the only changes are ـُ → ـَ and the loss of ن.

الأَفْعالُ الخَمْسَةُ on their own, because they are the half of the lesson you can actually hear:

The particles, one example each. The bold word is the verb they have bent.

Weak-final verbs. Two of the three types show the fatḥa; the third has nowhere to put it.

The same three across the cells you will meet most. The duals are left out; they follow the masculine plural in dropping the ن: يَمْشِيَا، يَدْعُوَا، يَنْسَيَا. Note that the dual يَدْعُوَا and the plural يَدْعُوا come out with the same letters - only the fatḥa on the و tells them apart, and in the dual that alif is a real long vowel, not the silent one.

Examples

Common mistakes

• لَنْ أَذْهَبُ -> لَنْ أَذْهَبَ - لَنْ is a subjunctive particle, so the ḍamma must become a fatḥa. Leaving the indicative ending is the single commonest slip in this lesson.
• أُريدُ أَنْ أَذْهَبُ -> أُريدُ أَنْ أَذْهَبَ - the same fault after أَنْ. The first verb keeps its ḍamma; only the verb behind the particle changes.
• لَنْ يَذْهَبونَ -> لَنْ يَذْهَبوا - one of the five verbs, so the ن of الرَّفْع goes, and the silent alif is written in its place.
• لَنْ ذَهَبَ -> لَنْ يَذْهَبَ - لَنْ can only stand in front of an imperfect. To negate a past verb you need ما or لَمْ, which is lesson 37.
• أُريدُ أَنْ تَدْرُسينَ -> أُريدُ أَنْ تَدْرُسي - the feminine singular loses its ن exactly as the plurals do. The remaining ي is enough to mark the person.
• يَدْرُسو -> يَدْرُسوا - the أَلِف فارِقَة is compulsory in spelling even though it is never pronounced. There is no such thing as a verb ending in a bare و here.
• لَنْ يَمْشي -> لَنْ يَمْشِيَ - a verb in ـي does show the fatḥa, and it is genuinely pronounced. Only the ـى type (يَنْسى) stays unchanged.
• لَنْ يَنْسَ -> لَنْ يَنْسى - do not amputate the ألف مقصورة after لَنْ. Shortening the end of the verb is the jussive’s business (lesson 35), not the subjunctive’s.
• لِ أَشْتَرِيَ -> لِأَشْتَرِيَ - the لام of purpose is a prefix and is written joined, with no space, like the بِـ of bi- and the سَـ of the future.
• لَنْ الطُّلّابُ يَدْرُسوا -> لَنْ يَدْرُسَ الطُّلّابُ - nothing may come between the particle and its verb; a noun subject follows the verb.
• أُريدُ أَنْ لا تَذْهَبَ -> أُريدُ أَلّا تَذْهَبَ - أَنْ and لا fuse into one written word.
• الطّالِباتُ لَنْ يَدْرُسوا -> الطّالِباتُ لَنْ يَدْرُسْنَ - a group of women keeps ـْنَ in every mood, because that ن is the pronoun and not a mood marker.

Tips

• Learn the change as one sentence you can say to yourself: “fatḥa for the five bare cells, no ن for the five verbs, nothing at all for the two ـْنَ.” Thirteen cells, three instructions.
• Drill by pairs, out loud, indicative straight into subjunctive: يَدْرُسُ - يَدْرُسَ، تَدْرُسينَ - تَدْرُسي، يَدْرُسونَ - يَدْرُسوا. The pairing is what fixes it, not the list.
• Memorize the particles as a short chant - أَنْ، لَنْ، كَيْ، لِـ، حَتّى، إِذَنْ - and treat every one of them as a red flag telling your hand what to write on the end of the next verb.
• لَنْ is worth over-practising on its own. It is the highest-frequency member of the list, and it is the one place where an A2 learner is most likely to be heard making the mistake.
• When you write ـوا, say “wāw plus a silent alif” in your head. The alif is spelling, not sound, and treating it as a two-part unit stops you from dropping it.
• Watch out for the accidental lookalikes: تَمْشي is “she walks” in the indicative but “(that) you, one woman, walk” in the subjunctive, and يَدْعُوا (they) differs from يَدْعُوَ (he) by nothing but that silent alif. The sentence, not the shape, resolves them.
• Do not go hunting for the mood in an unvocalized newspaper. In ordinary Arabic writing the fatḥa is not printed at all, so what you look for is the particle in front and the missing ن behind.
• Ignore, for now, the question of when to prefer حَتّى over كَيْ, or أَنْ over a verbal noun. Get the ending right first; the choices arrive in lessons 38 and 54.