Understanding Weak Roots in Arabic Language: Assimilated, Hollow, Defective, and Doubly Weak Verbs

Quick Answer

A weak root is a root containing an original weak letter. This letter usually appears as wāw or yāʾ, although it may change into an alif or disappear in certain conjugations. A verb is called assimilated (mithāl) when the weak letter occurs at the beginning, hollow (ajwaf) when it occurs in the middle, and defective (nāqiṣ) when it occurs at the end. When the root contains two weak letters, it is classified as either separated doubly weak (lafīf mafrūq) or adjacent doubly weak (lafīf maqrūn), depending on their positions.

Introduction

Arabic learners often face a confusing moment when they discover that a single verb does not always preserve the form in which they first encountered it. They learn قَالَ (qāla: he said), then come across يَقُولُ (yaqūlu: he says), قُلْتُ (qultu: I said), and قُلْ (qul: say). At first, these forms may appear to be different verbs, even though they all belong to the same root: ق و ل.

This variation occurs because one of the root's original letters is weak. The weak letters in Arabic tend to change or disappear in certain morphological and phonological environments, so they do not remain equally visible in every conjugated form. The wāw or yāʾ may appear explicitly, change into an alif, or disappear when a suffix or jussive particle is added to the verb.

This is why understanding weak Arabic roots is so important. A learner who memorizes only قَالَ may hesitate when encountering قُلْتُ, while someone who knows that the root is ق و ل will recognize the relationship between them. The same applies to common verbs such as وَعَدَ (waʿada: he promised), بَاعَ (bāʿa: he sold), دَعَا (daʿā: he invited), and رَمَى (ramā: he threw). Weak roots also hide inside familiar nouns: see how they shape صَفَاء, وَفَاء, and حَيَاء in 20 Arabic words rich in meaning.

Describing these verbs as "weak" does not mean that they are incorrect or linguistically incomplete. It is a morphological term describing the nature of one of the original letters and the way it is affected during conjugation. Weak verbs are not all of one type. Their classification depends on the position of the weak letter. If it occurs at the beginning of the root, the verb is assimilated. If it occurs in the middle, the verb is hollow. If it occurs at the end, the verb is defective. Two weak letters may also occur within the same root, creating what Arab morphologists call a doubly weak verb.

This article explains the different types of weak Arabic roots through changes that can be seen and compared. The goal is not to collect as many rules as possible, but to learn how to uncover the original letter even when it changes or disappears.

What Is a Weak Root?

A weak root is a root in which one or more of the original letters is a weak letter. Examples include:

و ع د (w-ʿ-d) — associated with promising ق و ل (q-w-l) — associated with saying ر م ي (r-m-y) — associated with throwing

These roots appear in verbs such as:

The wāw in وَعَدَ remains visible, while the original wāw in قَالَ has changed into an alif in the past tense. The original yāʾ at the end of رَمَى, meanwhile, appears in the form of an alif maqṣūrah ى.

The root of a weak verb cannot therefore always be identified from the past-tense form alone. Sometimes we need the present tense, verbal noun, or another form that reveals the original letter.

What Are the Weak Letters in Arabic?

The weak letters are alif, wāw, and yāʾ: ا، و، ي

When writing a root, however, we need to be precise. The alif in words such as قَالَ and بَاعَ is not usually the original root letter. It is a surface form resulting from the transformation of a wāw or yāʾ.

Compare:

قَالَ — يَقُولُ — قَوْلٌ qāla — yaqūlu — qawlun "he said — he says — saying"

The forms يَقُولُ and قَوْلٌ reveal that the middle letter of the root is wāw: ق و ل

Now compare:

بَاعَ — يَبِيعُ — بَيْعٌ bāʿa — yabīʿu — bayʿun "he sold — he sells — selling"

The forms يَبِيعُ and بَيْعٌ reveal that the middle letter is yāʾ: ب ي ع

The alif visible in the past tense may therefore conceal an original wāw or yāʾ.

Why Does the Form of a Weak Letter Change?

The letters wāw and yāʾ are easily affected by surrounding vowels and letters. They may be difficult to pronounce in certain combinations, so their forms change according to the rules of weak-letter transformation, known in Arabic morphology as iʿlāl.

Common changes include:

• Changing wāw or yāʾ into an alif.
• Deleting the weak letter.
• Transferring its vowel to the preceding letter.
• Restoring the original letter when a pronoun is attached to the verb.

Consider the following change:

قَالَ → قُلْتُ

In قَالَ, the middle letter appears as a long alif. When the subject suffix tāʾ is attached, the vowel becomes short:

قُلْتُ — qultu — "I said"

Another change appears in:

دَعَا → لَمْ يَدْعُ

The final weak letter is deleted when the present-tense verb becomes jussive after لَمْ:

لَمْ يَدْعُ أَحَدًا. lam yadʿu aḥadan "He did not invite anyone."

These changes are not random, but they vary according to the position of the weak letter and the form of the verb.

What Are the Types of Weak Arabic Roots?

Arab morphologists classify weak roots according to the position of the weak letter:

This table provides the basic map for understanding weak verbs. Instead of memorizing every change as a separate case, we begin by locating the weak letter within the root.

What Is the Assimilated Verb?

An assimilated verb, called mithāl in Arabic morphology, is a verb whose first original letter is weak, as in و ع د. The verb is وَعَدَ (waʿada — he promised).

The wāw remains visible in the past tense:

وَعَدْتُ صَدِيقِي بِالْمُسَاعَدَةِ. waʿadtu ṣadīqī bil-musāʿadati "I promised my friend that I would help."

In this verb, however, the wāw is deleted in the present tense (يَعِدُ — yaʿidu — he promises) and in the imperative (عِدْ — ʿid — promise).

Another example is:

وَصَلَ — يَصِلُ — صِلْ waṣala — yaṣilu — ṣil "he arrived — he arrives — arrive"

يَصِلُ القِطَارُ فِي السَّاعَةِ التَّاسِعَةِ. yaṣilu al-qiṭāru fī al-sāʿati al-tāsiʿati "The train arrives at nine o'clock."

The deletion of wāw should not be turned into a rule applied to every verb beginning with wāw or yāʾ in every pattern. Some verbs retain the weak letter, and augmented forms behave differently. The best approach is to learn the past and present forms together.

What Is the Hollow Verb?

A hollow verb, called ajwaf, is a verb whose middle root letter is weak. One example is ق و ل. The verb is قَالَ (qāla — he said).

The original wāw appears in the present tense and verbal noun: يَقُولُ (yaqūlu — he says) and قَوْلٌ (qawlun — saying / statement).

The long alif, however, becomes a short vowel when certain vowel-bearing subject pronouns are attached to the past-tense verb: قُلْتُ (qultu — I said).

For example:

قَالَتْ لَيْلَى الحَقِيقَةَ. — qālat Laylā al-ḥaqīqata — "Layla told the truth."

قُلْتُ لَهُ الحَقِيقَةَ. — qultu lahu al-ḥaqīqata — "I told him the truth."

The middle root letter may also be yāʾ, as in ب ي ع:

بَاعَ — يَبِيعُ — بِعْتُ — بِعْ bāʿa — yabīʿu — biʿtu — biʿ "he sold — he sells — I sold — sell"

بَاعَ التَّاجِرُ البِضَاعَةَ. — bāʿa al-tājiru al-biḍāʿata — "The merchant sold the goods."

Not every hollow verb takes the same short vowel. We say قُلْتُ, but بِعْتُ. The actual conjugation of each verb must therefore be learned rather than applying the vowel of one hollow verb to every other verb in the category.

What Is the Defective Verb?

A defective verb, called nāqiṣ, is a verb whose final original letter is weak. The final root letter may be wāw, as in د ع و (دَعَا — daʿā — he invited / called), or yāʾ, as in ر م ي (رَمَى — ramā — he threw).

Certain forms reveal the original letter clearly:

دَعَوْتُ أَصْدِقَائِي إِلَى العَشَاءِ. — daʿawtu aṣdiqāʾī ilā al-ʿashāʾi — "I invited my friends to dinner."

رَمَيْتُ الكُرَةَ نَحْوَ الهَدَفِ. — ramaytu al-kurata naḥwa al-hadafi — "I threw the ball toward the goal."

The final letter is deleted when the present-tense verb becomes jussive:

لَمْ يَدْعُهُمْ إِلَى الاِجْتِمَاعِ. — lam yadʿuhum ilā al-ijtimāʿi — "He did not invite them to the meeting."

لَمْ يَرْمِ الطِّفْلُ الحَجَرَ. — lam yarmi al-ṭiflu al-ḥajara — "The child did not throw the stone."

The same deletion occurs in the masculine singular imperative:

اُدْعُ صَدِيقَكَ. — udʿu ṣadīqaka — "Invite your friend."

اِرْمِ الكُرَةَ. — irmi al-kurata — "Throw the ball."

The ḍammah in اُدْعُ and the kasrah in اِرْمِ are not weak letters. They are short vowels that remain after the final root letter has been deleted.

What Is the Separated Doubly Weak Verb?

A doubly weak root contains two weak letters. It is called separated when a sound consonant stands between them. One example is و ق ي. The first letter is wāw, the final letter is yāʾ, and qāf stands between them.

For example:

وَقَى المِعْطَفُ الطِّفْلَ مِنَ البَرْدِ. — waqā al-miʿṭafu al-ṭifla mina al-bardi — "The coat protected the child from the cold."

يَقِي هَذَا السِّتَارُ الغُرْفَةَ مِنَ الشَّمْسِ. — yaqī hādhā al-sitāru al-ghurfata mina al-shamsi — "This curtain protects the room from the sun."

قِ نَفْسَكَ مِنَ الخَطَرِ. — qi nafsaka mina al-khaṭari — "Protect yourself from danger."

This word family illustrates how extensively a weak verb may change. The initial wāw is deleted in the present tense, and the final yāʾ is then deleted in the imperative. Consequently, only one sound consonant and a short vowel remain visible in قِ.

This does not mean that the verb's root has been reduced to one letter. Its root remains و ق ي.

What Is the Adjacent Doubly Weak Verb?

A doubly weak verb is called adjacent when its two weak letters occur next to one another within the root. One example is ط و ي, where wāw and yāʾ are adjacent.

For example:

طَوَى الطَّالِبُ الوَرَقَةَ. — ṭawā al-ṭālibu al-waraqata — "The student folded the paper."

يَطْوِي العَامِلُ القُمَاشَ بِعِنَايَةٍ. — yaṭwī al-ʿāmilu al-qumāsha biʿināyatin — "The worker folds the fabric carefully."

Another example is ر و ي:

رَوَى — يَرْوِي — rawā — yarwī — "he narrated — he narrates"

رَوَى الجَدُّ قِصَّةً قَدِيمَةً. — rawā al-jaddu qiṣṣatan qadīmatan — "The grandfather narrated an old story."

With an adjacent doubly weak verb, both weak letters must be tracked together because changes at the end of the verb can make the relationship between the past tense and the root less obvious.

How Can We Identify a Hidden Original Letter?

When an alif appears in the past-tense verb, we cannot determine from the past tense alone whether its original form was wāw or yāʾ. We need another form that reveals it.

Using the Present Tense: قَالَ → يَقُولُ — the wāw reveals that the root is ق و ل. بَاعَ → يَبِيعُ — the yāʾ reveals that the root is ب ي ع.

Using the Verbal Noun: قَالَ → قَوْلٌ and بَاعَ → بَيْعٌ.

Using the First-Person Past Tense: دَعَا → دَعَوْتُ (the original wāw reappears) and رَمَى → رَمَيْتُ (the original yāʾ reappears).

Using the Word Family:

سَعَى — يَسْعَى — سَعْيٌ saʿā — yasʿā — saʿyun "he strove — he strives — striving"

The verbal noun سَعْيٌ reveals that the root is س ع ي.

When learning weak verbs, it is therefore better not to record the past tense alone. Add the present tense and verbal noun—or the first-person form when necessary—to uncover the original letter.

How Are Weak Words Weighed?

A weak word is weighed according to its original form before the weak-letter transformation, while also accounting for the change that has occurred.

The Pattern of قَالَ. The root is ق و ل. The underlying morphological structure of قَالَ corresponds to فَعَلَ. The wāw carried a vowel and was preceded by a fatḥah, so it changed into an alif. The pattern is therefore قَالَ — فَعَلَ. We do not treat the alif as an original root letter corresponding to ʿayn, because the original letter is wāw.

The Pattern of بَاعَ. The root is ب ي ع. Its pattern is بَاعَ — فَعَلَ. The original yāʾ is the middle radical, although it appears as an alif in the past tense.

The Pattern of يَدْعُو. The root is د ع و. We match dāl with fāʾ, ʿayn with ʿayn, and wāw with lām: يَدْعُو — يَفْعُلُ.

The Pattern of لَمْ يَرْمِ. The original form is يَرْمِي, and its pattern is يَفْعِلُ. When the verb becomes jussive, its weak final radical is deleted. The lām of the pattern is therefore deleted as well: لَمْ يَرْمِ — لَمْ يَفْعِ.

This method shows the effect of deletion instead of ignoring it and makes clear that the omitted letter remains part of the root.

Do All Weak Verbs Conjugate in the Same Way?

No. Classification helps us anticipate where a change may occur, but it does not replace learning the individual verb.

With an initial-wāw assimilated verb, we find وَعَدَ — يَعِدُ (waʿada — yaʿidu — "he promised — he promises"). However, wāw is not deleted from every verb beginning with it or from every morphological form.

Hollow verbs also differ in their short vowels:

قَالَ — يَقُولُ — قُلْتُ — qāla — yaqūlu — qultu — "he said — he says — I said" بَاعَ — يَبِيعُ — بِعْتُ — bāʿa — yabīʿu — biʿtu — "he sold — he sells — I sold" نَامَ — يَنَامُ — نِمْتُ — nāma — yanāmu — nimtu — "he slept — he sleeps — I slept"

We cannot produce قُلْتُ, بِعْتُ, or نِمْتُ from the past-tense form alone unless we know the verb's morphological class.

It is therefore useful to memorize small sets such as قَالَ — يَقُولُ — قُلْتُ — قُلْ instead of memorizing only قَالَ = said.

What Is the Difference Between Weak and Hamzated Verbs?

A hamzated verb is not weak merely because it contains a hamzah. In morphological classification, hamzah is a sound consonant, although it has its own spelling and pronunciation rules.

For example, س أ ل (سَأَلَ — saʾala — he asked) is a hamzated root, but it is not weak because it does not contain an original wāw or yāʾ. Another example is أ خ ذ (أَخَذَ — akhadha — he took), which has a hamzah as its first radical. It is not an assimilated weak verb.

The confusion is increased by the fact that an alif may carry a hamzah, as in أَخَذَ, or appear as the result of a weak-letter transformation, as in قَالَ. The two cases are different: أ in the first word is an original hamzah, while the alif in the second represents an original wāw.

How Can You Learn Weak Verbs in Practice?

Learn the Basic Conjugation Set

Do not record the past tense alone. Use four forms when necessary:

Classify the Verb According to the Position of the Weak Letter

Ask: Does the weak letter occur at the beginning? In the middle? At the end? Does the root contain two weak letters? The answer identifies the part of the verb you should monitor during conjugation.

Connect Every Change to a Sentence

لَمْ يَقُلْ شَيْئًا. — lam yaqul shayʾan — "He did not say anything." لَمْ يَبِعِ التَّاجِرُ السَّيَّارَةَ. — lam yabiʿi al-tājiru al-sayyārata — "The merchant did not sell the car." لَمْ يَمْشِ الطِّفْلُ وَحْدَهُ. — lam yamshi al-ṭiflu waḥdahu — "The child did not walk alone."

Do Not Mix Modern Standard Arabic with Dialect

Weak verbs also occur in Arabic dialects, but their vowels and endings may differ from those of Modern Standard Arabic. If your goal is to learn Modern Standard Arabic, memorize its standard forms first, then study the dialectal forms separately.

Did You Know?

An Arabic imperative may consist visibly of only one sound consonant, as in:

قِ نَفْسَكَ. — qi nafsaka — "Protect yourself."

The form قِ, however, does not have a one-letter root. It comes from the triliteral root و ق ي. The initial wāw was deleted in the present tense, and the final yāʾ was then deleted when the imperative was formed, leaving only a qāf with a kasrah. This example clearly demonstrates that the visible word does not always display every letter of its root.

Summary

• A weak root contains one or more original weak letters.
• Weak letters may appear as alif, wāw, or yāʾ, but an alif may originate from either wāw or yāʾ.
• An assimilated verb is weak in its first radical, as in وَعَدَ.
• A hollow verb is weak in its middle radical, as in قَالَ and بَاعَ.
• A defective verb is weak in its final radical, as in دَعَا and رَمَى.
• A separated doubly weak verb contains two weak letters separated by a sound consonant, as in وَقَى.
• An adjacent doubly weak verb contains two adjoining weak letters, as in طَوَى.
• The present tense, verbal noun, and first-person past form can help reveal the original letter.
• A hamzated verb is not weak unless it also contains an original weak letter.
• The best approach is to learn the past, present, and other important conjugated forms together.

Frequently Asked Questions

What Does It Mean for a Root to Be Weak?

It means that one or more of its original letters is a weak letter. This letter may change or disappear in certain conjugated forms.

Is the Alif an Original Root Letter in قَالَ?

No. The root of قَالَ is ق و ل. Forms such as يَقُولُ and قَوْلٌ reveal the original wāw. The alif in the past tense results from weak-letter transformation.

How Can I Tell Whether an Alif Comes from Wāw or Yāʾ?

Consult the present tense, verbal noun, or first-person past form. We say قَالَ — يَقُولُ, revealing an original wāw, and بَاعَ — يَبِيعُ, revealing an original yāʾ.

Why Is the Wāw Deleted from يَعِدُ?

Because وَعَدَ is an initial-wāw assimilated verb. Its wāw is deleted in the present tense according to this verb's morphological structure. The same deletion appears in its imperative: عِدْ.

Why Do We Say قُلْتُ Rather Than قَالْتُ?

The middle letter of a hollow verb becomes short when certain vowel-bearing subject pronouns are attached. قَالَ therefore becomes قُلْتُ when the first-person tāʾ is added.

Is a Defective Verb Incomplete?

No. "Defective" is a morphological term indicating that the weak letter occurs at the end of the root. It does not mean that the verb is incomplete in meaning or incorrect.

What Is the Difference Between Separated and Adjacent Doubly Weak Verbs?

In a separated doubly weak root, a sound consonant separates the two weak letters, as in و ق ي. In an adjacent doubly weak root, the two weak letters occur next to one another, as in ط و ي.

Is Hamzah a Weak Letter?

No. In morphological classification, hamzah is a sound consonant. سَأَلَ is therefore a hamzated verb, not a weak verb.

Track the Hidden Letter with Rooto

Visit the Rooto Machine and click SPIN. When a word appears, do not begin by translating it. Look at its root and ask whether it contains a wāw or yāʾ.

If the root is weak, identify the position of the weak letter and classify it: is it assimilated, hollow, defective, or doubly weak? Then pronounce the displayed word and try to predict another form that reveals the original letter. After five spins, note the category in which you made the most mistakes and return to its section in this guide.

References Used

1. Al-Rajihi, Abduh. Applied Morphology (al-Taṭbīq al-Ṣarfī). Dar al-Nahda al-Arabiyya for Printing and Publishing, Beirut, 1973.
2. Ryding, Karin C. (2005). A Reference Grammar of Modern Standard Arabic. Cambridge University Press.