In short

Every Arabic verb has a noun that names its action: كَتَبَ “he wrote” has كِتابَةٌ “writing”, اِسْتَخْدَمَ “he used” has اِسْتِخْدامٌ “use”. That noun is the مَصْدَر, and Arabic reaches for it constantly where English would use a gerund, an infinitive, or a whole subordinate clause. Signs, headlines, contracts and academic prose are built out of مَصادِر: الدُّخولُ مَمْنوعٌ، التَّدْخينُ مُضِرٌّ، اِسْتِمْرارُ الحِوارِ.

There are two of them. The plain one - المَصْدَر الصَّريح - is a single word from the dictionary. The clausal one - المَصْدَر المُؤَوَّل - is the أَنْ clause you already build in lesson 34: أُريدُ أَنْ أَذْهَبَ. Arabic treats those two as the same grammatical object, so you can swap one for the other, and that swap is the practical skill of this lesson. Once you can turn أَنْ أَذْهَبَ into الذَّهابَ you have a second register available in every sentence you write.

The rule

1. What a مَصْدَر is. It is a noun, not a verb form. It names the action in the abstract, with no person, no tense and no mood attached: قِراءَةٌ is “reading” as such, not “I read” or “he was reading”. Because it is a noun it takes ال, takes tanwīn, takes case endings, takes adjectives, and can be the مُبْتَدَأ, the خَبَر, the فاعِل, the مَفْعول بِه, or the noun after a preposition - anything a noun can be.

2. Form I: the مَصْدَر is lexical. For the simple triliteral verb there is no reliable rule. The shape must be learned with the verb, exactly as you learn the plural of a noun. كَتَبَ gives كِتابَةٌ but دَخَلَ gives دُخولٌ and فَهِمَ gives فَهْمٌ, and nothing in the three radicals predicts which. When you meet a new Form I verb, write down three things: الماضي، المُضارِع، المَصْدَر. Dictionaries print all three for exactly this reason.

3. The Form I families are worth recognizing, not deriving. A handful of shapes cover most of what you will read, and there are loose tendencies: verbs of craft and occupation like كِتابَة and زِراعَة tend to فِعالَة; verbs of coming and going like دُخول and خُروج tend to فُعول. Treat those as recognition aids for guessing at a word you half-remember, never as a licence to invent one. The table below gives the frequent families with real pairs.

4. From Form II upward the مَصْدَر is predictable. This is the good news, and it is most of the lesson’s practical value: each derived form has a regular مَصْدَر shape - point 5 below names the two places where a second shape competes - and you can build it from the verb without a dictionary. Learn a hook word for each row of the derived table - تَدْريس، مُشاهَدَة، إِرْسال، تَعَلُّم، تَعاوُن، اِنْكِسار، اِجْتِماع، اِسْتِخْدام - and you have the whole system. Notice the internal signature of the last three: a kasra sits immediately before the long ا, which is what makes اِنْفِعال، اِفْتِعال، اِسْتِفْعال instantly recognizable on a page.

5. Two details inside the derived table. First, Form II is تَفْعيل, but when the third radical is weak (a ناقِص verb, lesson 51) the shape becomes تَفْعِلَة: رَبّى → تَرْبِيَةٌ، سَمّى → تَسْمِيَةٌ، صَفّى → تَصْفِيَةٌ. A few sound-rooted verbs took تَفْعِلَة lexically as well - جَرَّبَ → تَجْرِبَةٌ - so if a word looks like that shape, do not “correct” it. Second, Form III has two shapes: the regular مُفاعَلَة (شاهَدَ → مُشاهَدَةٌ، ساعَدَ → مُساعَدَةٌ) and a shorter فِعال that some verbs prefer or allow alongside it (دافَعَ → دِفاعٌ، حاوَرَ → حِوارٌ، حافَظَ → حِفاظٌ). The فِعال ones are frequent nouns in their own right; collect them as vocabulary.

6. The hamza tells you which form you are looking at. Form IV’s مَصْدَر إِفْعال begins with هَمْزَة قَطْع, written on a seat with a kasra: إِرْسالٌ، إِعْلامٌ، إِغْلاقٌ. Forms VII, VIII, IX and X begin with هَمْزَة وَصْل, the bare propping alif of lesson 48: اِنْكِسارٌ، اِجْتِماعٌ، اِسْتِخْدامٌ. This difference survives the stripping of the vowel marks, so it is visible in ordinary unvocalized text: إعلام is right and اعلام is wrong; استخدام is right and إستخدام is wrong. If you remember one spelling fact from this lesson, make it this one.

7. A مَصْدَر behaves like any other noun. It takes the definite article where English uses a bare gerund - التَّدْخينُ مَمْنوعٌ “smoking is forbidden” - and Arabic uses that definite form far more readily than English uses “the”. It declines normally: مَرْفوع as a subject, مَنْصوب as an object, مَجْرور after a preposition or as the second term of an إِضافَة. A few مَصادِر have even drifted into concrete countable nouns and take plurals: اِجْتِماعٌ / اِجْتِماعاتٌ “meeting(s)”, مُقابَلَةٌ / مُقابَلاتٌ “interview(s)”.

8. المَصْدَر المُؤَوَّل: a clause doing a noun’s job. Arabic can also build the same meaning out of a small clause, and the grammarians call that clause an interpreted مَصْدَر - a مَصْدَر in disguise. Two constructions do it:

• أَنْ + المُضارِع المَنْصوب, from lesson 34: أَنْ تَنْجَحَ = نَجاحُكَ. The verb after أَنْ is in the subjunctive, so it never carries a ḍamma: an ordinary verb takes a fatḥa, the forms that end in نُون drop it, and a verb ending in ى shows no change at all.
• أَنَّ + اسْم مَنْصوب + خَبَر, from lesson 44: أَنَّ الطّالِبَ ناجِحٌ = نَجاحُ الطّالِبِ.

There is a third, less obvious member: أَنْ + الماضي, which is common after time words - خَرَجْنا بَعْدَ أَنِ انْتَهَى الدَّرْسُ. (Note the kasra on أَنِ there: it is a helping vowel before the silent وَصْل alif of اِنْتَهى, exactly as in هَلِ اسْتَخْدَمْتَ.)

Keep أَنْ and أَنَّ apart by what follows: أَنْ takes a verb, أَنَّ takes a noun. The two are not interchangeable, and mixing them is a very common error in this area.

9. Swapping the two, and the case that results. To convert a clause into a plain مَصْدَر: take the verb’s مَصْدَر, attach the subject as a pronoun suffix or as the second term of an إِضافَة, and give the noun the case of the slot the clause was filling. The clause itself shows no ending - that is precisely why the swap is worth practising, because it forces you to name the slot.

• Subject slot → مَرْفوع: يَسُرُّني أَنْ تَنْجَحَ → يَسُرُّني نَجاحُكَ.
• Object slot → مَنْصوب: أُريدُ أَنْ أَذْهَبَ → أُريدُ الذَّهابَ.
• After a preposition, or after ظَرْف like قَبْلَ and بَعْدَ → مَجْرور: دَرَسْتُ لِأَنْجَحَ → دَرَسْتُ لِلنَّجاحِ; وَصَلَ قَبْلَ أَنْ نَخْرُجَ → وَصَلَ قَبْلَ خُروجِنا.

10. Which one to use. Both are correct and both are current; the difference is texture. The أَنْ clause is the everyday spoken-formal choice and fits almost anywhere a plain مَصْدَر would, even when you cannot recall the مَصْدَر of the verb - the exception being verbs that report a fact (عَلِمَ، سَمِعَ), which want أَنَّ with a noun rather than أَنْ with a verb. The plain مَصْدَر is denser and more written: press headlines, official notices and academic prose prefer it because it packs a whole clause into a single noun, and because a notice or a headline often has no room for a verb at all - مَمْنوعٌ التَّدْخينُ، اِسْتِمْرارُ الحِوارِ. Read for the صَريح, speak with the مُؤَوَّل, and you will be idiomatic in both directions.

11. What this lesson leaves to others. A مَصْدَر can carry its own object, either in an إِضافَة or in the accusative, and it can be described by an adjective while it does so; that whole construction is lesson 67, and every example here is deliberately built without it. The مَصْدَر used to intensify its own verb - دَرَسَ دِراسَةً جادَّةً - is المَفْعول المُطْلَق, lesson 60. The مَصادِر of derived forms built on weak roots (تَمَنّى → تَمَنٍّ) and the rarer المَصْدَر الميمِيّ are beyond this step.

Forms & patterns

A note on the tables: the وَزْن column shows a bare template, and a bare template carries no case ending - فِعالَة، فُعول، تَفْعيل are pattern names, not words. Every real word is printed with its full ending, and takes whatever case its sentence gives it.

Form I - the frequent families, with the verb they belong to:

Those six shapes are not the whole list - Form I has dozens - but they cover the great majority of the verbs you have met so far.

The derived forms, one shape each:

Form IX, the colour verbs, follows اِفْعِلال: اِحْمَرَّ → اِحْمِرارٌ. It is rare enough to leave at that.

Watch the vowel that sits before the last radical: تَفَعُّل has a ḍamma (تَعَلُّمٌ) and so does تَفاعُل (تَعاوُنٌ), while the past-tense verbs they come from have a fatḥa (تَعَلَّمَ، تَعاوَنَ).

The two clausal types, and their plain equivalents:

And the case the plain noun then carries, which is decided by the slot, not by the noun:

Examples

Common mistakes

• الكُتوبُ صَعْبٌ -> الكِتابَةُ صَعْبَةٌ - Form I’s مَصْدَر cannot be built from a template. Reaching for the فُعول of دُخول and خُروج gives كُتوبٌ, which is not a word. كَتَبَ happens to take كِتابَةٌ, and the only way to know that is to have learned the verb with its مَصْدَر.
• إِسْتِخْدامُ الحاسوبِ -> اِسْتِخْدامُ الحاسوبِ - the alif of اِسْتِفْعال is هَمْزَة وَصْل and is written bare, never with a seat. The same for اِجْتِماع، اِنْكِسار، اِسْتِقْبال.
• ارْسالٌ سَريعٌ -> إِرْسالٌ سَريعٌ - Form IV goes the other way: its مَصْدَر starts with a real هَمْزَة قَطْع on a seat. Pair the two in memory - إِعْلام with a seat, اِسْتِعْلام without.
• أُريدُ أَنْ أَذْهَبُ -> أُريدُ أَنْ أَذْهَبَ - أَنْ puts the following مُضارِع in the مَنْصوب (lessons 33 and 34). A ḍamma there is not a small slip; it means the clause is no longer a مَصْدَر مُؤَوَّل at all.
• أُريدُ الذَّهابُ -> أُريدُ الذَّهابَ - when you swap the clause for a plain noun, the noun must take the case of the slot. Here it is the object of أُريدُ, so مَنْصوب.
• يَسُرُّني نَجاحَكَ -> يَسُرُّني نَجاحُكَ - same rule, opposite outcome: this مَصْدَر is the فاعِل of يَسُرُّ, so مَرْفوع. Always ask what job the clause was doing before you choose an ending.
• أَنَّ تَنْجَحَ -> أَنْ تَنْجَحَ - أَنْ is followed by a verb, أَنَّ by a noun in the accusative. Use أَنَّكَ ناجِحٌ if you want the shadda.
• أُحِبُّ التَّعْليمَ (meaning “I like learning”) -> أُحِبُّ التَّعَلُّمَ - تَعْليم is Form II, what the teacher does; تَعَلُّم is Form V, what the student does. The مَصْدَر inherits the meaning of its form, so picking the wrong form picks the wrong meaning.
• تَرْبيٌ -> تَرْبِيَةٌ - a Form II verb with a weak final radical takes تَفْعِلَة, not تَفْعيل. Same for تَسْمِيَة، تَصْفِيَة.
• اِجْتَماعٌ طَويلٌ -> اِجْتِماعٌ طَويلٌ - the مَصْدَر of Form VIII is اِفْتِعال with a kasra on the ت, even though the verb اِجْتَمَعَ has a fatḥa there. That kasra before the long ا is the signature of VII, VIII and X alike.

Tips

• Store every new Form I verb as a triple in your notes: كَتَبَ / يَكْتُبُ / كِتابَةٌ. Adding the مَصْدَر later, from memory, almost never works.
• For the derived forms, memorize one hook word per row of the table rather than the abstract pattern. تَدْريس، مُشاهَدَة، إِرْسال، تَعَلُّم، تَعاوُن، اِنْكِسار، اِجْتِماع، اِسْتِخْدام is eight words and it is the whole system.
• A quick self-test on the derived side: cover the مَصْدَر column and rebuild it from the verb. If you can do that for eight verbs, you can do it for eight hundred.
• Turn the swap into a daily drill. Take any أَنْ sentence you wrote and rewrite it with a plain مَصْدَر, saying out loud which slot it fills and therefore which ending it takes.
• If the مَصْدَر escapes you mid-sentence, use the أَنْ clause. Almost anywhere a plain مَصْدَر fits, the clause fits too - a working escape hatch, not a second-best.
• Read headlines. Arabic press headlines are chains of مَصادِر, so ten minutes of front pages will give you more of these nouns in context than any list.
• Leave for later: مَصادِر that carry their own objects (lesson 67), the intensifying مَفْعول مُطْلَق (lesson 60), and the مَصادِر of derived forms on weak roots. Sound roots first.