Verb Classes and the Six Unaugmented Triliteral Patterns

1. Triliteral and quadriliteral roots

A triliteral has three root consonants:
ضَرَبَ — ḍ-r-b, he struck.
فَتَحَ — f-t-ḥ, he opened.
A quadriliteral has four root consonants:
بَعْثَرَ — b-ʿ-th-r, he scattered.
The number of visible letters in an inflected verb is not a reliable root count by itself. Separate person/tense markers and derivational additions to identify the original radicals.

2. Unaugmented and augmented forms

An unaugmented (mujarrad) verb has no extra derivational consonants beyond its basic root pattern, as in نَصَرَ (faʿala).
An augmented (mazīd fīhi) verb adds one or more letters to the root within a derived stem.
اِجْتَنَبَ comes from j-n-b with added i- and -t- in its stem.
اِسْتَنْصَرَ comes from n-ṣ-r with the prefixed ist- sequence.
Augmentation may modify the meaning, but a derivational pattern does not guarantee one mechanical translation for all roots.

3. Four primary morphological classes

Combining root length and augmentation yields four principal groups:

Word / formMeaning / explanation
Triliteral unaugmentedthree radicals, no derivational additions: نَصَرَ.
Triliteral augmentedthree radicals with added letters: اِجْتَنَبَ.
Quadriliteral unaugmentedfour radicals without additions: دَحْرَجَ.
Quadriliteral augmentedfour radicals plus added letters: تَزَلْزَلَ.

The root of تَزَلْزَلَ is z-l-z-l; the leading tāʾ is added. Five visible letters do not imply a five-radical root.

4. The six triliteral-unaugmented classes

The six standard triliteral unaugmented classes are distinguished primarily by the vowel of the second radical in the perfect and imperfect:

Word / formMeaning / explanation
نَصَرَ يَنْصُرُfaʿala yafʿulu.
ضَرَبَ يَضْرِبُfaʿala yafʿilu.
سَمِعَ يَسْمَعُfaʿila yafʿalu.
فَتَحَ يَفْتَحُfaʿala yafʿalu.
كَرُمَ يَكْرُمُfaʿula yafʿulu.
حَسِبَ يَحْسِبُfaʿila yafʿilu.

A perfect form alone may fit multiple classes: learn its imperfect alongside it.

5. The fāʾ–ʿayn–lām template

In the schematic root فَعَلَ, fāʾ, ʿayn and lām represent the first, second and third radicals. They are called fāʾ al-kalimah, ʿayn al-kalimah and lām al-kalimah.
For نَصَرَ, nūn is the first, ṣād the second and rāʾ the third radical.
For سَمِعَ, sīn, mīm and ʿayn occupy these places.
For ضَرَبَ, they are ḍād, rāʾ and bāʾ.
The decisive vowel for these classes is the second radical's vowel in the perfect/imperfect pair.

6. Class 1: naṣara–yanṣuru

نَصَرَ — يَنْصُرُ — نَصْرًا
He helped — he helps — helping/support.
This class is فَعَلَ يَفْعُلُ. The second radical takes fatḥah in the perfect and ḍammah in the imperfect: naṣara / yanṣuru.
Further verbs following the same pairing include دَخَلَ يَدْخُلُ (enter) and تَرَكَ يَتْرُكُ (leave).
The radicals remain the same; the distinguishing feature is the vowel pairing, not the introduction of a new root.

7. The short paradigm for class 1

نَصَرَ — يَنْصُرُ — نَصْرًا
Active perfect: he helped; active imperfect: he helps; verbal noun: helping.
نَاصِرٌ — مَنْصُورٌ
Active participle: helper; passive participle: the one helped.
اُنْصُرْ — لَا تَنْصُرْ
Imperative: help! Prohibition: do not help!
نُصِرَ — يُنْصَرُ
Passive perfect and imperfect: he was helped / he is helped.
The root is constant across voice, verbal nouns, participles, commands and prohibitions.

8. Class 2: ḍaraba–yaḍribu

ضَرَبَ — يَضْرِبُ — ضَرْبًا
He struck — he strikes — striking.
The class is فَعَلَ يَفْعِلُ. The second radical has fatḥah in the perfect, then kasrah in the imperfect: ḍaraba / yaḍribu.
غَسَلَ يَغْسِلُ — washed / washes.
جَلَسَ يَجْلِسُ — sat / sits.
Both this class and naṣara have the perfect pattern faʿala. Their different imperfect vowels distinguish their classes.

9. The short paradigm for class 2

ضَرَبَ — يَضْرِبُ — ضَرْبًا
He struck — he strikes — striking.
ضَارِبٌ — مَضْرُوبٌ
One who strikes — one who was struck.
اِضْرِبْ — لَا تَضْرِبْ
Strike! — Do not strike!
ضُرِبَ — يُضْرَبُ
He was struck — he is struck.
The imperative اِضْرِبْ has an initial connecting hamzah with kasrah, unlike اُنْصُرْ in the naṣara class. This difference follows the imperfect pattern.

10. Why naṣara and ḍaraba differ

Both classes have فَعَلَ as the perfect, so their imperfects distinguish them:
نَصَرَ ← يَنْصُرُ — ḍammah on the second radical in the imperfect: yafʿulu.
ضَرَبَ ← يَضْرِبُ — kasrah on the second radical: yafʿilu.
The imperatives اُنْصُرْ and اِضْرِبْ consequently differ in their initial hamzah vowel.
If you know only that a verb has perfect faʿala, you cannot always determine the class without its attested imperfect.

11. Class 3: samiʿa–yasmaʿu

سَمِعَ — يَسْمَعُ — سَمْعًا
He heard — he hears — hearing.
Its pattern is فَعِلَ يَفْعَلُ: the second radical has kasrah in the perfect and fatḥah in the imperfect, samiʿa / yasmaʿu.
عَلِمَ يَعْلَمُ — knew / knows.
فَهِمَ يَفْهَمُ — understood / understands.
The kasrah of the perfect distinguishes this class from the perfect forms of naṣara and ḍaraba, both on faʿala.

12. The short paradigm for class 3

سَمِعَ — يَسْمَعُ — سَمْعًا
He heard — he hears — hearing.
سَامِعٌ — مَسْمُوعٌ
Listener/hearer — something heard.
اِسْمَعْ — لَا تَسْمَعْ
Listen! — Do not listen!
سُمِعَ — يُسْمَعُ
It was heard — it is heard.
The mīm has kasrah in the perfect samiʿa, but fatḥah in yasmaʿu and the related imperative/prohibition. Correct identification of the vowel pair explains the derived command form.

13. Class 4: fataḥa–yaftaḥu

فَتَحَ — يَفْتَحُ — فَتْحًا
He opened — he opens — opening.
The second radical carries fatḥah in both perfect and imperfect; the pattern is فَعَلَ يَفْعَلُ.
مَنَعَ يَمْنَعُ — prevented / prevents.
ذَهَبَ يَذْهَبُ — went / goes.
The imperfect of samiʿa also has fatḥah on the second radical, but samiʿa has perfect faʿila whereas fataḥa has faʿala. The full vowel pairing determines the class.

14. The short paradigm for class 4

فَتَحَ — يَفْتَحُ — فَتْحًا
He opened — he opens — opening.
فَاتِحٌ — مَفْتُوحٌ
One who opens — opened.
اِفْتَحْ — لَا تَفْتَحْ
Open! — Do not open!
فُتِحَ — يُفْتَحُ
It was opened — it is opened.
The instrument مِفْتَاحٌ (key) comes from this same root f-t-ḥ. The verbal noun fatḥ names the action; miftāḥ names an implement used to perform it.

15. Contrasting samiʿa and fataḥa

Both samiʿa and fataḥa have imperfect يَفْعَلُ, yet different perfects:
سَمِعَ يَسْمَعُ — kasrah on the second radical in the perfect, fatḥah in the imperfect.
فَتَحَ يَفْتَحُ — fatḥah on that radical in both forms.
Therefore the imperfect يَسْمَعُ must not be classified as the fataḥa class solely because it matches yafʿalu. The complete verb pair identifies the class.
The verbal nouns also need to be learned as attested forms: سَمْعٌ and فَتْحٌ.

16. Class 5: karuma–yakrumu

كَرُمَ — يَكْرُمُ — كَرَمًا
He became noble/generous — he is noble/generous — nobility or generosity.
This class is فَعُلَ يَفْعُلُ, with ḍammah on the second radical in both perfect and imperfect.
حَسُنَ يَحْسُنُ — was/became good.
قَرُبَ يَقْرُبُ — was/became near.
Verbs of this class often describe qualities or states, so adjectives such as كَرِيمٌ are natural expressions of the quality involved.

17. Quality verbs in class 5

كَرُمَ يَكْرُمُ كَرَمًا centres on generosity or nobility, and كَرِيمٌ is a familiar adjective meaning noble or generous.
كَرُمَ is not كَرَّمَ: the first is unaugmented class 5, while the second is the augmented Form II meaning to honour someone.
Many verbs in this class describe states and are typically intransitive. Not every mechanically imaginable passive participle or instrument form is equally established in ordinary Arabic. A conjugational template should not be confused with proof of common lexical usage.

18. Class 6: ḥasiba–yaḥsibu

حَسِبَ — يَحْسِبُ — حَسْبًا وَحِسَابًا
He counted/calculated — he counts/calculates — counting or calculation.
Its pattern is فَعِلَ يَفْعِلُ: the second radical has kasrah in both perfect and imperfect.
The sīn in ḥasiba and yaḥsibu therefore keeps kasrah.
This is the textbook's chosen vocalised paradigm. Arabic roots can have attested alternative vocalisations or meanings in some usages; the pair shown here is the one to analyse for this class.

19. The short paradigm for class 6

حَسِبَ — يَحْسِبُ — حَسْبًا وَحِسَابًا
He counted — he counts — counting/calculation.
حَاسِبٌ — مَحْسُوبٌ
Calculator/accountant — something counted or calculated.
اِحْسِبْ — لَا تَحْسِبْ
Calculate! — Do not calculate!
حُسِبَ — يُحْسَبُ
It was calculated — it is calculated.
Both samiʿa and ḥasiba have faʿila as their perfect, but samiʿa takes yafʿalu while ḥasiba takes yafʿilu as the imperfect.

20. Same perfect, different imperfect

سَمِعَ — يَسْمَعُ and حَسِبَ — يَحْسِبُ both have kasrah on the second radical in the perfect, but differ in the imperfect.
Samiʿa class: فَعِلَ يَفْعَلُ — kasrah → fatḥah.
Ḥasiba class: فَعِلَ يَفْعِلُ — kasrah → kasrah.
The same contrast affects the second radical in their commands, اِسْمَعْ and اِحْسِبْ. The class therefore cannot be established solely from the perfect form or from the word's translation.

21. All six patterns in one comparison

The six triliteral unaugmented pairs are:
فَعَلَ يَفْعُلُ — نَصَرَ يَنْصُرُ
فَعَلَ يَفْعِلُ — ضَرَبَ يَضْرِبُ
فَعِلَ يَفْعَلُ — سَمِعَ يَسْمَعُ
فَعَلَ يَفْعَلُ — فَتَحَ يَفْتَحُ
فَعُلَ يَفْعُلُ — كَرُمَ يَكْرُمُ
فَعِلَ يَفْعِلُ — حَسِبَ يَحْسِبُ
Each imperfect belongs with the preceding perfect as an attested pair. Mixing the vowels of unrelated forms creates an invalid class assignment.

22. Verbal nouns and their classes

A maṣdar is a verbal noun that names an action or state without specifying a person or tense. The verbal nouns of unaugmented triliteral verbs do not all follow one compulsory pattern; attested usage is important.
نَصَرَ — نَصْرٌ: helping.
ضَرَبَ — ضَرْبٌ: striking.
سَمِعَ — سَمْعٌ: hearing.
فَتَحَ — فَتْحٌ: opening.
كَرُمَ — كَرَمٌ: nobility/generosity.
حَسِبَ — حِسَابٌ: calculation.
Learning a verb's class does not eliminate the need to learn its proper verbal noun.

23. Paradigm templates versus attested words

In a short conjugational paradigm, the textbook combines perfect, imperfect, maṣdar, active/passive participles, passive forms, imperatives and prohibitions; some patterns also display schematic place/time, instrument and comparative nouns.
For نَصَرَ — يَنْصُرُ — نَاصِرٌ — مَنْصُورٌ, the common senses are straightforward. But not every hypothetical instrument or setting noun formed by a template is necessarily a widely attested word.
A formation rule describes how a pattern can be built; attested usage establishes whether a particular lexical item is actually employed.

24. Reliable identification of a verb class

To identify a triliteral unaugmented class reliably:
1. Identify the three radicals, separating any derivational extras.
2. Read the fully vocalised third-person masculine singular perfect.
3. Check the attested third-person masculine singular imperfect.
4. Compare the second radical's vowels with the six class patterns.
For example, عَلِمَ يَعْلَمُ has kasrah then fatḥah on lām (its second radical), making it the samiʿa class rather than the fataḥa class.

25. Additional source-table forms: setting, instrument and comparative

The source’s short paradigms also present a place/time noun, an instrument noun, and a comparative with its feminine, in addition to the perfect, imperfect, maṣdar, participles, imperative and prohibition. The remaining source-table slots are:

Word / formMeaning / explanation
Naṣaraمَنْصَرٌ، مِنْصَرٌ، أَنْصَرُ، نُصْرَى.
Ḍarabaمَضْرِبٌ، مِضْرَبٌ، أَضْرَبُ، ضُرْبَى.
Samiʿaمَسْمَعٌ، مِسْمَعٌ، أَسْمَعُ، سُمْعَى.
Fataḥaمَفْتَحٌ، مِفْتَحٌ، أَفْتَحُ، فُتْحَى.
Karumaمَكْرَمٌ، مِكْرَمٌ، أَكْرَمُ، كُرْمَى.
Ḥasibaمَحْسَبٌ، مِحْسَبٌ، أَحْسَبُ، حُسْبَى.

These are morphological templates presented for practice. Being derivable by analogy does not ensure a particular noun is common in idiomatic Arabic; established lexical usage must be assessed separately.