In short

Arabic builds a condition out of three parts and no more: a word that opens it, the verb of the condition, and the answer. إِنْ تَدْرُسْ تَنْجَحْ - “if you study, you will pass”. English marks the two halves with if and a future tense; Arabic marks them by reshaping the two verbs, and the reshaping is the مَجْزوم you already own from lesson 35, now working twice in one sentence and with no negation anywhere in sight.

The lesson turns on a single split. Most conditional words - إِنْ and the “who/what/when/where” family - put both verbs into the jussive. Two of the commonest, إِذا and كُلَّما, govern nothing at all and take a past-tense form even when the meaning is the future. Add the فَ that certain answers demand and real conditions are finished. Unreal ones - “if I had known”, “were it not for” - run on لَوْ and لَوْلا and are lesson 65; do not borrow them here.

The rule

1. The three parts. Every conditional sentence is أَداةُ الشَّرْطِ (the conditional word) + فِعْلُ الشَّرْطِ (the verb of the condition) + جَوابُ الشَّرْطِ (the answer, also called جَزاءُ الشَّرْطِ). The whole thing is one sentence and the أَداة stands at its head; nothing goes in front of it except a connector such as وَ or a topic phrase. No comma is required between the two halves - modern editing often puts a ، there, but nothing grammatical hangs on it; the boundary is the end of the first verb’s clause.

2. Two families, and this is the whole lesson. أَدَواتُ الشَّرْطِ split into those that cause جَزْم and those that do not.

• الجازِمَة - إِنْ، مَنْ، ما، مَهْما، مَتى، أَيْنَما، كَيْفَما، أَيّ. Both verbs go into the مَجْزوم: إِنْ تَدْرُسْ تَنْجَحْ.
• غَيْرُ الجازِمَة - إِذا and كُلَّما. Nothing is put into any mood; the verb after them is normally a past-tense form: إِذا دَرَسْتَ نَجَحْتَ.

Those two example sentences translate identically into English (“if/when you study, you will pass”) and share not one grammatical feature. Learn them as a matched pair and half the errors in this area never happen.

3. إِنْ: two jussives, and the second one is the surprise. After إِنْ the verb of the condition takes the جَزْم exactly as it does after لَمْ. What is new is that the answer takes it too, although no particle stands in front of the answer at all:

إِنْ تَجْتَهِدْ (شَرْط، مَجْزوم) تَنْجَحْ (جَواب، مَجْزوم).

Nothing negates, nothing prohibits, nothing orders; the sukūn on تَنْجَحْ is caused by the conditional structure alone. Two verbs, two sukūns, one إِنْ.

4. Where the جَزْم is actually visible. On a sound verb the mark is a bare sukūn and unvocalized text hides it completely. On the other classes the word visibly shrinks, and those are the forms to drill - a reader hears your mistake there:

• الصَّحيحُ السّالِمُ: تَدْرُسُ → تَدْرُسْ. A sukūn replaces the ḍamma.
• النّاقِص (weak final letter): تَمْشي → تَمْشِ. The ي is deleted and its kasra stays.
• الأَجْوَف (weak middle letter): تَزورُ → تَزُرْ. The long و shortens to a ḍamma.
• الأَفْعالُ الخَمْسَةُ: تَدْرُسونَ → تَدْرُسوا. The نون drops, the silent alif is written.

5. Past-tense forms inside a jussive frame. After إِنْ you may equally use a past-tense verb, and this is very common in writing: إِنْ دَرَسْتَ نَجَحْتَ. The past form is مَبْنِيّ - built, unchangeable - so nothing visible happens to it; the grammarians say it is فِي مَحَلِّ جَزْمٍ, in the position of a jussive. Mixing is allowed in one direction: a past شَرْط with a jussive جَواب is good Arabic (إِنْ دَرَسْتَ تَنْجَحْ). The reverse - a jussive شَرْط with a past جَواب - is not something to produce; keep to the three frames in the table below.

6. إِذا: the past form that means the future. إِذا is not a governing particle at all. Arabic grammar classes it as a time word (ظَرْف) carrying conditional force, and a time word puts nothing into a mood. Its verb is a past-tense form and its time reference is the future:

إِذا وَصَلَ القِطارُ رَكِبْنا مَعًا. - “When the train arrives we will get on together.”

Two proofs that إِذا governs nothing. First, a present-tense verb in the answer keeps its ḍamma untouched: إِذا زارَني صَديقي أُقَدِّمُ لَهُ القَهْوَةَ. Second, when you do see a sukūn after إِذا it always has another cause - إِذا لَمْ تَفْهَمْ فَاسْأَلْ: that sukūn belongs to لَمْ, which is a jussive particle in its own right. In modern prose إِذا is followed directly by its verb; you will also meet إِذا ما, where the ما adds nothing to the meaning.

7. إِنْ or إِذا - a real difference in meaning. They are not stylistic variants.

• إِذا = the speaker expects it to happen, or knows it will: إِذا جاءَ الصَّيْفُ سافَرْنا. It is “when” as much as “if”, and it is by far the commoner of the two in modern prose.
• إِنْ = the speaker is genuinely unsure, or thinks it unlikely: إِنْ تَتَغَيَّرْ خُطَّتُهُمْ نُخْبِرْكَ. It is the hypothetical “if”, and it dominates conditions with لَمْ, formal writing and set phrases such as إِنْ شاءَ اللهُ.

8. The rest of the جازِمَة family: they hold a job inside the clause. إِنْ is a particle and does nothing else. The others are nouns or adverbs, so besides opening the condition they fill a slot in it - subject, object, place, manner:

• مَنْ “whoever”, for people: مَنْ يَعْمَلْ بِجِدٍّ يَنَلْ ما يُريدُ.
• ما and مَهْما “whatever”, for things; مَهْما is the emphatic one and cannot refer to a person: مَهْما تَقُلْ فَلَنْ أُغَيِّرَ رَأْيي.
• مَتى “whenever”: مَتى تَصِلْ إِلى المَطارِ أَسْتَقْبِلْكَ. Same word as the question مَتى؟ “when?”, different job - here it is not a question and takes no question mark.
• أَيْنَما “wherever” and كَيْفَما “however, in whatever way”: أَيْنَما تَذْهَبْ تَجِدْ أَصْدِقاءَ.
• أَيّ “whichever”, which is unique in taking a following noun in إِضافَة and in changing its own ending according to its role: أَيُّ طالِبٍ يَجْتَهِدْ يَنْجَحْ (مُبْتَدَأ، مَرْفوع) beside أَيَّ كِتابٍ تَقْرَأْ تَسْتَفِدْ مِنْهُ (مَفْعول بِهِ، مَنْصوب).

9. فاءُ الجَوابِ - the فَ that is not optional. A jussive or a past-tense answer attaches directly with nothing between: إِنْ تَدْرُسْ تَنْجَحْ، إِذا دَرَسْتَ نَجَحْتَ. But some answers cannot be a jussive at all, and Arabic then requires فَـ glued to the front of the answer. The list is short and worth memorizing as a list:

1. the answer is a nominal sentence: إِذا نَجَحْتَ فَلَكَ جائِزَةٌ.
2. the answer is an imperative (or a prohibition with لا): إِذا وَصَلْتَ فَاتَّصِلْ بي.
3. the answer opens with سَـ / سَوْفَ: إِنْ تَحْضُرْ فَسَنَبْدَأُ فَوْرًا.
4. the answer opens with قَدْ: إِنْ تَسْأَلْهُ فَقَدْ يُساعِدُكَ.
5. the answer opens with ما: إِنْ تَبْحَثْ عَنْهُ فَما هُوَ هُنا.
6. the answer opens with لَنْ: مَهْما تَقُلْ فَلَنْ أُغَيِّرَ رَأْيي.

One test covers all six: if the answer cannot itself be put into the jussive, it needs the فَ. A noun has no mood; an imperative is already fixed; سَـ، سَوْفَ، قَدْ، ما، لَنْ each block the jussive by occupying the slot in front of the verb. The same applies to the frozen verbs لَيْسَ and عَسى: إِذا تَأَخَّرَ فَلَيْسَ ذٰلِكَ خَطَأَهُ. Because إِذا so often introduces a nominal or a future answer, you will see فَ with إِذا constantly - but the فَ belongs to the answer’s shape, not to إِذا.

10. Negating inside a condition. “If … not” is إِنْ لَمْ or إِذا لَمْ plus a jussive; لَمْ does the work, so the pattern is identical either way: إِنْ لَمْ تُسافِرْ غَدًا فَاتَّصِلْ بي، إِذا لَمْ تَفْهَمِ الدَّرْسَ فَاسْأَلِ المُعَلِّمَ. The compact alternative is وَإِلّا “otherwise”, which packs وَ + إِنْ + لا into one word and drops the verb of the condition - so its own verb still comes out مَجْزوم: اُدْرُسْ وَإِلّا تَرْسُبْ.

11. Two sukūns cannot meet - the same repair as in lesson 35. A jussive ending in a sukūn followed by the article takes a kasra: كَيْفَما تُعامِلِ النّاسَ يُعامِلوكَ، إِذا لَمْ تَفْهَمِ الدَّرْسَ. This is pronunciation repair only; the verb is still مَجْزوم.

12. What is deliberately left out. لَوْ and لَوْلا - the unreal conditions, “if you had studied you would have passed” - are lesson 65 in full, and using لَوْ for a real, open condition is the single commonest mistake in this area. كُلَّما as a time expression was lesson 38 and appears here only to sit in the جازِمة / غَيْر جازِمة column. Linking whole paragraphs with فِي حالِ، شَريطَةَ أَنْ، بِشَرْطِ أَنْ belongs to lesson 66. And the older أَدَوات إِذْما، أَنّى، حَيْثُما، أَيّانَ are jussive-causing too but uncommon in modern prose - recognise them, do not produce them. Of the four only حَيْثُما “wherever” is still met with any regularity.

Forms & patterns

The particles, sorted by the only thing that matters. The last two rows are the ones that govern nothing:

The jussive across the verb classes, so that the mark is visible somewhere. Second person masculine singular, since that is the form a condition usually lands on:

The doubled verb is added for completeness only: it behaves as in lesson 35, where the three permitted shapes were laid out.

The three frames you should actually produce. Everything else is recognition:

When فاءُ الجَوابِ is compulsory - the whole list, with the trigger in bold:

Examples

Common mistakes

• إِنْ تَدْرُسُ تَنْجَحُ -> إِنْ تَدْرُسْ تَنْجَحْ - إِنْ is jussive-causing and it reaches both verbs. Two ḍammas here is the single commonest error in the whole topic.
• إِذا تَدْرُسُ تَنْجَحُ -> إِذا دَرَسْتَ نَجَحْتَ - إِذا takes a past-tense form even though the meaning is future. A present-tense verb straight after إِذا does occur in Classical Arabic (إِذا تُتْلى عَلَيْهِ آياتُنا), but it is rare; in modern prose write the past form.
• إِذا نَجَحْتَ لَكَ جائِزَةٌ -> إِذا نَجَحْتَ فَلَكَ جائِزَةٌ - the answer is a nominal sentence, so فاءُ الجَوابِ is obligatory. Dropping it leaves two sentences stuck together.
• إِذا وَصَلْتَ اِتَّصِلْ بي -> إِذا وَصَلْتَ فَاتَّصِلْ بي - an imperative answer needs the same فَ. It is glued to the verb, never written as a separate word.
• مَهْما تَقُلْ لَنْ أُغَيِّرَ رَأْيي -> مَهْما تَقُلْ فَلَنْ أُغَيِّرَ رَأْيي - لَنْ blocks the jussive, so the answer takes the فَ. Same for سَـ، سَوْفَ، قَدْ، ما.
• لَوْ تَدْرُسْ تَنْجَحْ -> إِنْ تَدْرُسْ تَنْجَحْ - لَوْ is for conditions the speaker treats as unreal or already lost. For an open, still-possible condition use إِنْ or إِذا.
• إِنْ تَزورْني أَزورْكَ -> إِنْ تَزُرْني أَزُرْكَ - a sukūn cannot follow a long vowel, so the hollow verb shortens in the jussive: تَزورُ becomes تَزُرْ.
• إِنْ تَمْشي تَصِلْ -> إِنْ تَمْشِ تَصِلْ - in a final-weak verb the ي is deleted outright and only its kasra remains. The word really is that short.
• إِنْ تَدْرُسونَ تَنْجَحونَ -> إِنْ تَدْرُسوا تَنْجَحوا - the الأَفْعالُ الخَمْسَةُ drop their نون in the jussive, in the answer just as in the condition.
• إِذا لَمْ تَفْهَمَ الدَّرْسَ -> إِذا لَمْ تَفْهَمِ الدَّرْسَ - لَمْ demands a sukūn (not the fatḥa of the subjunctive), and the sukūn turns into a kasra before the article.

Tips

• Learn إِنْ تَدْرُسْ تَنْجَحْ and إِذا دَرَسْتَ نَجَحْتَ as one flashcard with two faces. Everything else in this lesson is an expansion of that contrast.
• A shortcut for choosing: if you would naturally say “when” in English, write إِذا; if you would insist on “if”, write إِنْ. In modern prose إِذا wins most of the time.
• Do not practise conditions on sound verbs alone - إِنْ تَدْرُسْ hides its own grammar in unvocalized text. Build your sentences on زارَ، قالَ، مَشى، رَأى، اِسْتَطاعَ, where the collapse of the form is impossible to fake.
• Whenever you write إِذا, look at your answer clause before you finish the sentence. If it starts with a noun, a command, سَـ، سَوْفَ، قَدْ، ما or لَنْ, the فَ goes in. That check alone removes a whole class of errors.
• The negative frame إِنْ لَمْ / إِذا لَمْ is worth drilling on its own, because it stacks two jussive-causing words and learners routinely leave the ending open.
• Keep لَوْ out of your production entirely until lesson 65. If you are unsure whether a condition is real, it is real - unreal ones are the ones the speaker treats as contrary to fact.
• Read newspaper editorials for إِذا: it opens a great many sentences there, and seeing it followed by a past-tense verb fifty times will fix the pattern faster than any table.
• Ignore for now the archaic إِذْما، أَنّى، حَيْثُما and any classical example where a noun sits between إِذا and its verb. Modern written Arabic nearly always puts the verb straight after the particle.