نسي — forget with defective morphology and object or أن complements | Arabic (Modern Standard) Grammar

نَسِيَ “forget” is a final-weak Form-I verb from root ن-س-ي. Its basic complements are easy to understand, but they encode an important contrast: نسي المفتاح forgets a thing, نسي أنْ يغلق الباب forgets to perform an action, and نسي أنَّه أغلق الباب forgets the fact that he already closed it.

Its morphology changes visibly across نَسِيَ، يَنْسَى، لَمْ يَنْسَ، اِنْسَ. Attached pronouns introduce another alternation: ينساه in the indicative, but لم ينسه in the jussive. Learning those forms together prevents the two most persistent spelling errors with this verb.

Lookup card: نَسِيَ — يَنْسَى

Part	Verified form	Function
root and Form	ن-س-ي، Form I	final-weak in yāʾ
perfect, 3 m.sg.	نَسِيَ	he forgot
imperfect, 3 m.sg.	يَنْسَى	he forgets
imperative, 2 m.sg.	اِنْسَ	forget!
maṣdar	نِسْيَانٌ	forgetting; forgetfulness
active participle	نَاسٍ؛ النَّاسِي	forgetting / one who forgets
passive participle	مَنْسِيٌّ	forgotten; neglected
passive	نُسِيَ — يُنْسَى	was / is forgotten

The indefinite active participle is ناسٍ in nominative and genitive contexts; final yāʾ returns in الناسي and accusative ناسيًا. It is grammatically regular for this class but less useful than the finite verb. By contrast, passive participle منسي is common for a person, place, or issue that has been forgotten or neglected.

نسيت هاتفي في السيارة وعدت لأخذه.

nasītu hātifī fī s-sayyārati wa-ʿudtu liʾakhdhih.

I left my phone in the car and went back to get it. (Formal neutral.)

ينسى كريم الأسماء بسرعة، لكنه يتذكر الوجوه.

yansā karīmun l-ʾasmāʾa bisurʿatin, lakinnahu yatadhakkaru l-wujūh.

Karim forgets names quickly, but he remembers faces. (Formal neutral.)

💡

Use four anchors: نَسِيَ، يَنْسَى، لَمْ يَنْسَ، اِنْسَ. The long final ā belongs to the unsuffixed imperfect, while jussive and imperative delete it.

The defective paradigm

The perfect preserves yāʾ before consonant-initial suffixes: نَسِيتُ، نَسِينَا. It drops before masculine plural وا: نَسُوا. In the imperfect, unsuffixed singular ينسى alternates with forms such as feminine تنسين and plural ينسون.

Environment	Form	What changes
هو, perfect	نَسِيَ	root yāʾ visible
أنا / نحن, perfect	نَسِيتُ / نَسِينَا	yāʾ retained before suffix
هم, perfect	نَسُوا	yāʾ deleted before وا
هو, indicative	يَنْسَى	final sequence surfaces as ى / ā
أنتِ / هم, indicative	تَنْسَيْنَ / يَنْسَوْنَ	person endings expose other stem shapes
هو after لم	لَمْ يَنْسَ	jussive deletes final ى
أنتَ, command	اِنْسَ	imperative also lacks final ى

Indicative ينسى and subjunctive لن ينسى have the same surface long ā. Jussive لم ينسَ and prohibitive لا تنسَ show deletion. The pattern is shared with other final-weak verbs and is developed on the final-weak mood page.

لن ينسى السكان من ساعدهم بعد الفيضانات.

lan yansā s-sukkānu man sāʿadahum baʿda l-fayaḍānāt.

The residents will not forget those who helped them after the floods. (Formal.)

لم ينس المدير وعده بنشر النتائج كاملة.

lam yansa l-mudīru waʿdahu binashri n-natāʾiji kāmila.

The director did not forget his promise to publish the results in full. (Formal.)

لا تنس إغلاق النوافذ قبل أن تغادر.

lā tansa ʾighlāqa n-nawāfidhi qabla ʾan tughādir.

Do not forget to close the windows before you leave. (Formal neutral.)

The affirmative imperative “forget!” is meaningful in expressions such as انسَ الأمر “forget the matter / let it go.” Requests to remember usually use the prohibitive لا تنسَ, which is far more frequent than bare انسَ.

انس الأمر الآن، وسنبحث عن حل آخر غدا.

insa l-ʾamra l-ʾāna, wa-sa-nabḥathu ʿan ḥallin ʾākhara ghadan.

Forget it for now; we will look for another solution tomorrow. (Formal neutral.)

Forget a thing: direct objects and clitics

The forgotten person, object, name, appointment, or fact can be a direct object: نسي الاسم، نسي الموعد، نسي ما حدث. Neutral MSA does not need English-like about before this object. Some dialects use prepositional patterns; do not carry them unlabelled into formal writing.

نسيت موعد الطبيب حتى وصلني التنبيه.

nasītu mawʿida ṭ-ṭabībi ḥattā waṣalanī t-tanbīh.

I forgot the doctor’s appointment until the reminder reached me. (Formal neutral.)

لا أنسى ما فعله زملائي من أجل عائلتي.

lā ʾansā mā faʿalahu zumalāʾī min ʾajli ʿāʾilatī.

I do not forget what my colleagues did for my family. (Formal neutral.)

Attached object pronouns follow the verb directly. With a long-ā imperfect, a suffix changes written ى to standing ا: ينسى + ه = ينساه. After لم, deletion has already applied, so the result is لم ينسه, not لم ينساه.

Context	Form	Meaning
perfect + object	نَسِيتُهُ	I forgot it / him
indicative + object	يَنْسَاهُ	he forgets it / him
jussive + object	لَمْ يَنْسَهُ	he did not forget it / him
prohibition + object	لَا تَنْسَهُ	do not forget it / him
imperative + object	اِنْسَهُ	forget it / him

كتبت العنوان في دفتري كي لا أنساه.

katabtu l-ʿunwāna fī daftarī kay lā ʾansāh.

I wrote the address in my notebook so that I would not forget it. (Formal neutral.)

قرأ التقرير مرة واحدة، لكنه لم ينسه.

qaraʾa t-taqrīra marratan wāḥidatan, lakinnahu lam yansah.

He read the report once, but he did not forget it. (Formal neutral.)

💡

With an attached object, spelling reveals mood: ينساه has long ā, but لم ينسه and لا تنسه have short a after the final weak radical is deleted.

نسي أنْ يفعل: forget to perform an action

أَنْ + subjunctive imperfect presents an intended or expected action as an event. With نسي, it normally means the subject failed to remember to perform that action. The subject of both verbs is usually the same unless context supplies another interpretation.

نسيت أن أرسل الفاتورة إلى قسم المحاسبة.

nasītu ʾan ʾursila l-fātūrata ʾilā qismi l-muḥāsaba.

I forgot to send the invoice to the accounting department. (Formal.)

نسي الحارس أن يقفل الباب الخلفي.

nasiya l-ḥārisu ʾan yaqfila l-bāba l-khalfiyy.

The guard forgot to lock the back door. (Formal neutral.)

Arabic also permits a maṣdar object such as نسي إغلاق الباب. It can describe failure to remember the action, but أنْ + verb is often clearer when tense, negation, or additional complements make the action clause complex.

نسي أنَّ...: forget a fact

أَنَّ + clause packages a proposition as the forgotten fact. The attached subject pronoun is common: أنه، أنها، أنني. Unlike أنْ, أنَّ does not make the following verb subjunctive; it introduces a nominal clause whose predicate may contain an ordinary finite verb.

نسي أنه أرسل الفاتورة بالفعل، فأرسلها مرة ثانية.

nasiya ʾannahu ʾarsala l-fātūrata bil-fiʿli, fa-ʾarsalahā marratan thāniya.

He forgot that he had already sent the invoice, so he sent it a second time. (Formal neutral.)

نسيت أنني وعدت سارة بالاتصال مساء.

nasītu ʾannanī waʿadtu sārata bil-ittiṣāli masāʾ.

I forgot that I had promised Sara I would call in the evening. (Formal neutral.)

The English contrast is sharp: forgot to send implies that sending did not occur, while forgot that he had sent says it did occur but left memory. Arabic marks that contrast overtly with أنْ versus أنَّ.

Passive, participle, and collocations

Passive نُسِيَ — يُنْسَى backgrounds the person who forgot. It is useful in institutional prose, where an omission matters more than the individual responsible. منسي often develops the stronger implication “neglected, left out of public attention.”

نسي اسم أحد المشاركين عند إعداد القائمة النهائية.

nusiya smu ʾaḥadi l-mushārikīna ʿinda ʾiʿdādi l-qāʾimati n-nihāʾiyya.

One participant’s name was forgotten when the final list was prepared. (Formal passive.)

لا تزال القرى البعيدة جزءا منسيا من خطة التنمية.

lā tazālu l-qurā l-baʿīdatu juzʾan mansiyyan min khuṭṭati t-tanmiya.

The remote villages remain a neglected part of the development plan. (Formal.)

Collocation	Meaning and register
نَسِيَ الِاسْمَ / الْمَوْعِدَ	forget the name / appointment (neutral)
نَسِيَ أَنْ يَفْعَلَ	forget to do (neutral)
نَسِيَ أَنَّهُ فَعَلَ	forget that he did (neutral)
لَا تَنْسَ أَنَّ...	do not forget that... (neutral/formal reminder)
طَوَاهُ النِّسْيَانُ	it passed into oblivion (literary)
فِي غَيَاهِبِ النِّسْيَانِ	in the depths of oblivion (literary)

Common Mistakes

Keeping alif maqṣūra after لم

❌ لم ينسى خالد الموعد.

Incorrect—the singular jussive after لم deletes final ى.

✅ لم ينس خالد الموعد.

lam yansa khālidun l-mawʿid.

Khalid did not forget the appointment.

Keeping long ā before an object clitic in the jussive

❌ أخبرته بالموعد، لكنه لم ينساه.

Incorrect in the jussive after لم: final-weak deletion gives ينسه. The indicative ينساه is valid without لم.

✅ أخبرته بالموعد، لكنه لم ينسه.

ʾakhbartuhu bil-mawʿidi, lakinnahu lam yansah.

I told him about the appointment, but he did not forget it.

Using أنَّ for an unperformed action

❌ نسي أنه يغلق الباب قبل المغادرة.

Wrong for the intended meaning ‘he forgot to close’: أنَّ presents a fact or proposition, not an unperformed infinitival action. The sentence could be interpreted differently in a suitable context.

✅ نسي أن يغلق الباب قبل المغادرة.

nasiya ʾan yughliqa l-bāba qabla l-mughādara.

He forgot to close the door before leaving.

Adding عن before the forgotten thing

❌ نسيت عن موعد الاجتماع.

Nonstandard in neutral MSA for ‘I forgot the meeting time’; formal نسي takes the forgotten thing directly. Similar prepositional phrasing occurs in some dialects.

✅ نسيت موعد الاجتماع.

nasītu mawʿida l-ijtimāʿ.

I forgot the meeting time.

Key Takeaways

نَسِيَ — يَنْسَى is final-weak Form I from root ن-س-ي.
Jussive and masculine-singular imperative delete final ى: لم ينسَ، لا تنسَ، انسَ.
A forgotten thing is direct: نسي الموعد، نسيه.
With clitics, compare indicative ينساه with jussive لم ينسه.
نسي أنْ يفعل means “forgot to do”; نسي أنَّه فعل means “forgot that he did.”
Passive نُسِيَ and adjective منسي are useful when the forgotten agent is irrelevant or the sense shades into neglect.

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