In short

Lessons 46-48 sorted verbs by their pattern - what is added around the root. This lesson sorts them the other way, by the root letters themselves. Three letters cause trouble when you try to build a word on them: the hamza ء, a radical that is repeated, and the weak letters و and ي. Everything else conjugates like كَتَبَ and always has.

The good news first: the endings you learned in lessons 14, 22 and 41 never change. أَنا always ends in ـتُ in the past and starts with أَ in the present; هُمْ is always ـوا / ـونَ. What changes is whether the stem survives the collision. This lesson names all seven root classes so you can look at any verb and know what it is, then conjugates the three manageable ones: مَهْموز, مُضَعَّف and مِثال. The two genuinely difficult classes get lessons of their own immediately after.

The rule

1. Two families, seven classes. A root is صَحيح (“sound”) if none of its three letters is و or ي, and مُعْتَلّ (“weak”) if one or two of them are. Each family splits further, and the grammarians’ names are worth learning because dictionaries and grammars use them constantly:

• صَحيح سالِم - nothing special at all: كَتَبَ (ك-ت-ب)، دَرَسَ، جَلَسَ.
• صَحيح مَهْموز - one radical is a hamza: أَكَلَ (أ-ك-ل)، سَأَلَ (س-أ-ل)، قَرَأَ (ق-ر-أ).
• صَحيح مُضَعَّف - the second and third radicals are the same letter: مَدَّ (م-د-د)، رَدَّ.
• مُعْتَلّ مِثال - the first radical is و or ي: وَصَلَ (و-ص-ل)، يَبِسَ (ي-ب-س).
• مُعْتَلّ أَجْوَف - the middle radical is weak: قالَ (ق-و-ل)، باعَ (ب-ي-ع).
• مُعْتَلّ ناقِص - the last radical is weak: رَمى (ر-م-ي)، دَعا (د-ع-و).
• مُعْتَلّ لَفيف - two of the three are weak: وَقى (و-ق-ي)، طَوى (ط-و-ي).

Note where the hamza lands: ء is a consonant, so مَهْموز sits inside the sound family, not the weak one. It does not melt into a long vowel the way a و does; apart from a few frequent verbs (كُلْ، خُذْ، مُرْ in rule 4, and يَرى in rule 13) it only makes spelling hard.

2. Find the root first (lesson 22), then the class. Ask three questions in this order. Is one of the radicals ء? Are the second and third the same letter? Is the first, middle or last a و / ي? The answer tells you which paradigm to reach for, and it is why dictionaries print the root - قَرَأَ tells you nothing about يَقْرَأُ until you see ق-ر-أ.

3. مَهْموز الفاء: two hamzas contract into a مَدَّة. أَكَلَ conjugates completely normally in the past - أَكَلْتُ، أَكَلَتْ، أَكَلوا - and normally in the present too: يَأْكُلُ، تَأْكُلُ، نَأْكُلُ. The one form that breaks is أَنا, where the prefix أَ meets the root’s أْ. Arabic refuses هَمْزَتان in a row when the second one carries a sukūn: أَأْكُلُ becomes آكُلُ, written with a مَدَّة exactly as you learned in the pronunciation guide’s hamza lesson. The same contraction runs wherever a vowelled أ prefix meets a root hamza with a sukūn: آخُذُ، آمُرُ، آسَفُ، and Form IV آمَنَ / أُومِنُ (there أُ + ؤْ gives a long ū instead of a مَدَّة). Where the root hamza has a vowel of its own there is nothing to contract, and both hamzas stay: Form II أَثَّرَ → أُؤَثِّرُ.

4. Three imperatives throw the hamza away. The imperative is the jussive minus its prefix (lesson 36). For أَكَلَ that gives أْكُلْ, which begins with a hamza carrying a sukūn - and propping it up with a helping hamza would again give two in a row. So the root hamza is simply dropped: كُلْ، خُذْ، مُرْ. Only these three verbs do it. Others keep the hamza and seat it on a ئ after the helping kasra: أَذِنَ → اِئْذَنْ “give permission”. (After وَ or فَ, أَمَرَ recovers its full shape: وَأْمُرْ.)

5. مَهْموز العَيْن and مَهْموز اللّام: the letter stays, the seat moves. In سَأَلَ and قَرَأَ nothing is deleted and nothing contracts. The only difficulty is orthographic: which chair the hamza sits on. The seat follows the stronger of two vowels - the hamza’s own and the one before it - ranked kasra > ḍamma > fatḥa > sukūn:

• قَرَأَ (fatḥa on fatḥa) → أ; قَرَأْتُ (sukūn on fatḥa) → أ; يَقْرَؤونَ (ḍamma) → ؤ
• سَأَلَ، يَسْأَلُ، سَأَلْتُ → أ; the noun مَسْؤولٌ (ḍamma) → ؤ; سائِلٌ (kasra) → ئ
• one addition to the ladder: a sukūn ي in front of the hamza counts as a kasra → شَيْئًا، هَيْئَةٌ، يَيْئَسُ

سَأَلَ has a second, shorter imperative beside the regular اِسْأَلْ: سَلْ، سَلي، سَلوا. Both are fully standard modern Arabic: dictionaries cite اِسْأَلْ, and the short سَلْ is very common in speech and in print alike.

6. مُضَعَّف: the shadda holds until a sukūn arrives. م-د-د should give مَدَدَ, but two identical letters with a vowel between them collapse into one doubled letter: مَدَّ. That merger (إِدْغام) survives as long as whatever follows begins with a vowel:

مَدَّ، مَدَّتْ، مَدُّوا، يَمُدُّ، يَمُدّونَ، تَمُدّينَ

The moment an ending begins with a consonant - and in practice that means the sukūn-initial suffixes: the whole ـْتُ / ـْتَ / ـْتِ / ـْتُمْ set, plus ـْنا and ـْنَ - the two letters are forced apart again (فَكُّ الإِدْغام) and the buried third radical reappears:

مَدَدْتُ، مَدَدْنا، مَدَدْتُمْ، مَدَدْنَ - never *مَدَّتُ

This is the same trigger you met with كانَ → كُنْتُ in lesson 43, applied to a different weakness. The feminine plural does it in the present too: هُنَّ يَمْدُدْنَ, because ـْنَ carries a sukūn.

7. Which vowel comes back. When the letters split, the vowel between them is the verb’s own stem vowel from the dictionary: فَعَلَ verbs bring back a fatḥa (مَدَّ → مَدَدْتُ، رَدَّ → رَدَدْتُ), فَعِلَ verbs bring back a kasra (ظَلَّ → ظَلِلْتُ، مَلَّ → مَلِلْتُ). In the present the returning vowel is the مُضارِع vowel: يَمُدُّ → يَمْدُدْنَ، يَحُلُّ → يَحْلُلْنَ.

8. Doubled roots in the derived Forms behave identically. أَحَبَّ (Form IV of ح-ب-ب) gives أَحَبَّ، أَحَبَّتْ، أَحَبّوا، يُحِبُّ - but أَحْبَبْتُ، أَحْبَبْنا، أَحْبَبْتُمْ. So do اِسْتَعَدَّ → اِسْتَعْدَدْتُ، اِهْتَمَّ → اِهْتَمَمْتُ، اِسْتَمَرَّ → اِسْتَمْرَرْتُ.

9. مِثال: the و evaporates in the Form I present. This is the single most useful fact in the lesson. A verb whose first radical is و keeps it in the past and loses it in the مُضارِع:

وَصَلَ → يَصِلُ، وَجَدَ → يَجِدُ، وَقَفَ → يَقِفُ، وَعَدَ → يَعِدُ، وَزَنَ → يَزِنُ، وَضَعَ → يَضَعُ، وَهَبَ → يَهَبُ، وَسِعَ → يَسَعُ

Note وَضَعَ / يَضَعُ: the fatḥa is there because of the throaty ع, yet the و drops all the same. A tiny group of stative verbs keeps it - وَجِلَ / يَوْجَلُ “to be afraid”, وَدَّ / يَوَدُّ “to wish” - but they are rare enough to learn one by one when you meet them.

10. So the imperative of a مِثال is two letters long. Strip the prefix off تَصِلْ and the stem already begins with a consonant, so no helping hamza is needed at all: صِلْ، جِدْ، قِفْ، ضَعْ، عِدْ، زِنْ، صِفْ، هَبْ. A handful of nouns show the same loss with a ة sewn on the end to compensate: وَعَدَ → عِدَةٌ “a promise”، وَزَنَ → زِنَةٌ “a weight”، وَهَبَ → هِبَةٌ “a gift”.

11. Outside Form I the و is safe - except in Form VIII, where it becomes ت. Forms II, IV and X keep the و in plain sight: وَظَّفَ / يُوَظِّفُ، أَوْقَفَ / يُوقِفُ، اِسْتَوْرَدَ / يَسْتَوْرِدُ. Form VIII is different, because its ت infix lands immediately after the first radical: اِوْتَصَلَ is unpronounceable, so the و assimilates into the ت and the two merge under a shadda - اِتَّصَلَ. This produces a whole family of very common modern verbs: اِتَّصَلَ بِـ “contact”، اِتَّفَقَ عَلى “agree”، اِتَّحَدَ “unite”، اِتَّجَهَ إِلى “head for”، اِتَّسَعَ “widen”. اِتَّخَذَ “take, adopt” joins them from a hamzated root (أ-خ-ذ), by the same logic. Whenever you meet a verb beginning اِتَّـ, suspect a hidden و.

12. ي-initial roots do not drop anything. The rule above is about و only. Roots beginning with ي keep it right through: يَبِسَ / يَيْبَسُ “dry out”، يَئِسَ / يَيْئَسُ “despair”، يَسُرَ / يَيْسُرُ “become easy”. The doubled ي looks wrong and is correct. Luckily these verbs are few, because there is nothing to reason about here - you simply remember them.

13. Some verbs belong to two classes at once. رَأى is مَهْموز العَيْن and ناقِص (ر-أ-ي), and it loses the hamza outright in the present: يَرى، نَرى، أَرى. جاءَ is أَجْوَف and مَهْموز اللّام (ج-ي-أ). أَتى is مَهْموز الفاء and ناقِص (أ-ت-ي). لَفيف is the official name for one overlap only - two weak radicals in the same root, never a hamza plus a weak letter: وَقى (و-ق-ي) drops its و like a مِثال and ends like a ناقِص, which is how Arabic ends up with a one-letter imperative, قِ. Do not study any of these as a class; conjugate them by applying the two relevant rules in turn, and check the ones you use often.

14. Reading a doubled verb without vowel marks: count the letters. Unvocalized, مد can be مَدَّ “he stretched”, مُدَّ “stretch!”, or the noun مَدٌّ “extension, high tide”. But مدد has three consonants written out, so in a Form I verb it can only be the split stem - مَدَدْتُ، مَدَدْنا. (Outside Form I the same three letters can still be the noun مَدَدٌ “reinforcements” or the Form II verb مَدَّدَ “he extended”.) The letter count tells you whether a sukūn-initial ending is attached - a genuinely useful shortcut in unvocalized text.

15. Not in this lesson. The jussive of a doubled verb has three permitted shapes, لَمْ يَمُدَّ, لَمْ يَمُدِّ and لَمْ يَمْدُدْ - that was lesson 35, and nothing here changes it. Hollow verbs (قالَ، باعَ، نامَ) are lesson 50; verbs with a weak final radical (رَمى، دَعا، نَسِيَ) are lesson 51; and what all of these classes do in the passive - قيلَ، سُئِلَ، قُرِئَ - waits for lesson 52.

Forms & patterns

The seven classes at a glance

المَهْموز: the three positions

أَكَلَ in the مُضارِع - only أَنا is irregular; the duals and هُنَّ are left out because they add nothing new

مَدَّ in the past - the full set, because the split is the whole point

مَدَّ elsewhere, and two derived Forms

المِثال: the و goes missing in the present

The same root و across the Forms

Examples

Common mistakes

• أَأْكُلُ الفَطورَ -> آكُلُ الفَطورَ - Two hamzas cannot stand in a row. The prefix أَ plus the root’s أْ contract into a single letter with a مَدَّة.
• اُأْكُلْ الآنَ -> كُلِ الآنَ - كُلْ، خُذْ، مُرْ drop the root hamza in the imperative rather than propping it up. There is no helping hamza to add.
• قَرَئْتُ الكِتابَ -> قَرَأْتُ الكِتابَ - The seat follows the stronger of the hamza’s own vowel and the one before it. Here that is sukūn against fatḥa, so the chair is ا, not ي.
• سَئَلْتُ المُعَلِّمَ -> سَأَلْتُ المُعَلِّمَ - Same rule: fatḥa on fatḥa gives أ. A ئ needs a kasra somewhere in the pair, as in سائِلٌ or سُئِلَ.
• مَدَّتُ يَدي -> مَدَدْتُ يَدي - The ending ـْتُ begins with a sukūn, so the shadda has to split. (مَدَّتْ, with the sukūn on the ت, is the perfectly good “she stretched”.)
• أَحَبَّتُ هٰذِهِ المَدينَةَ -> أَحْبَبْتُ هٰذِهِ المَدينَةَ - Doubled roots split in the derived Forms exactly as in Form I; the doubling is a property of the root, not of the pattern.
• يَوْصِلُ القِطارُ -> يَصِلُ القِطارُ - The و of a Form I مِثال is deleted in the مُضارِع. Keeping it is the commonest error in this whole class.
• اِوْضَعِ الكِتابَ هُنا -> ضَعِ الكِتابَ هُنا - Take the prefix off تَضَعْ and the stem already starts with a consonant, so nothing needs to be added in front of it.
• اِنْتَصَلَ بي أَمْسِ -> اِتَّصَلَ بي أَمْسِ - Form VIII of و-ص-ل is not built with ن. The و merges into the ت of the pattern and the two are written as one doubled letter.
• يَبَسُ العُشْبُ في الصَّيْفِ -> يَيْبَسُ العُشْبُ في الصَّيْفِ - Only و-initial roots drop their first radical. A ي-initial root keeps it, doubled ي and all.

Tips

• Always in this order: find the root, name the class, then conjugate. Three quick questions - any hamza? any repeated radical? any و/ي, and where? - settle almost any verb you meet.
• One trigger runs through half of this lesson and all of lesson 50: does the ending begin with a sukūn? The culprits are the ت-endings (ـْتُ، ـْتَ، ـْتِ، ـْتُمْ) plus ـْنا and ـْنَ. Learn them as a set.
• Store مِثال verbs as pairs, وَصَلَ / يَصِلُ, never as single words - which is exactly why dictionaries print both. The present cannot be predicted from the past by ear.
• Memory hook for the imperatives: a مِثال command is about the shortest thing you can say in Arabic. صِلْ، قِفْ، ضَعْ، عِدْ - two letters, no prop, no prefix.
• Any modern verb starting اِتَّـ almost certainly hides a و: اِتَّصَلَ، اِتَّفَقَ، اِتَّجَهَ. Look under و-ص-ل، و-ف-ق، و-ج-ه in the dictionary, not under ا or ت.
• For the hamza seats, do not memorise a table - memorise the ladder kasra > ḍamma > fatḥa > sukūn and read the two vowels around the hamza.
• Ignore لَفيف as a category for now, and ignore رَأى، جاءَ، أَتى as puzzles. They are frequent enough that you will simply know them before you can analyse them.