لَيْسَ is the standard negative copula: it turns الجو معتدل “the weather is mild” into ليس الجو معتدلا “the weather is not mild.” Traditional analysis associates it with root ل-ي-س, but it is a frozen, exceptional verb rather than a productive Form-I lexical family. Its endings look like perfect-tense endings, yet its usual meaning is present: لَسْتُ متعبا means “I am not tired,” not “I was not tired.”
This page treats ليس as a lexical reference. For the wider affirmative system of كان وأخواتها, see كان in past-time clauses.
Lookup card: what exists and what does not
| Property | Verified form or behavior |
|---|---|
| Conventional root | ل-ي-س |
| Lexical class | irregular negative copula; historically perfect-shaped |
| 3 m.sg. | لَيْسَ |
| 1 sg. | لَسْتُ |
| Imperfect / imperative | none in contemporary MSA |
| Maṣdar / participles / passive | none in this negative-copula use |
| Basic frame | ليس + subject (nominative) + predicate (accusative) |
| Common marked frame | ليس + subject + بـ + predicate (formally genitive) |
The missing forms are a real lexical fact, not a gap to fill by analogy. There is no present يليس, command لِسْ, passive, or productive verbal noun meaning “not be.” For past and future negation, Arabic normally uses forms of كان: لم يكن “was not” and لن يكون “will not be.”
لست متأكدا من رقم القاعة
lastu mutaʾakkidan min raqmi l-qāʿa
I am not sure of the room number. (Formal neutral.)
لم يكن المكتب مفتوحا أمس
lam yakuni l-maktabu maftūḥan ʾams
The office was not open yesterday. (Past negation; use كان, not ليس.)
The complete agreement paradigm
Unlike an ordinary present-tense verb, ليس has no imperfect prefixes. Person, gender, and number are expressed with the same suffix set seen in the perfect:
| Person | Form | Person | Form |
|---|---|---|---|
| أنا | لَسْتُ | نحن | لَسْنَا |
| أنتَ | لَسْتَ | أنتِ | لَسْتِ |
| أنتما | لَسْتُمَا | أنتم | لَسْتُمْ |
| أنتنّ | لَسْتُنَّ | هو | لَيْسَ |
| هي | لَيْسَتْ | هما (m.) | لَيْسَا |
| هما (f.) | لَيْسَتَا | هم | لَيْسُوا |
| هنّ | لَسْنَ |
Notice the two stems: لَيْسـ in ليس، ليست، ليسا، ليستا، ليسوا, but لَسْـ in the consonant-suffixed forms لست، لسنا، لستن، لسن. English “is not / are not” changes only for number; Arabic also marks person and gender.
الطالبتان ليستا مسؤولتين عن الخطأ
aṭ-ṭālibatāni laysatā masʾūlatayni ʿani l-khaṭaʾ
The two female students are not responsible for the error. (Formal; subject-first dual agreement.)
المهندسات لسن مستعدات لتغيير التصميم
al-muhandisātu lasna mustaʿiddātin litaghyīri t-taṣmīm
The female engineers are not ready to change the design. (Formal; feminine plural.)
ليست النتائج نهائية بعد
laysati n-natāʾiju nihāʾiyyatan baʿd
The results are not final yet. (Formal verb-first order; a nonhuman plural triggers feminine-singular agreement.)
Subject nominative, predicate accusative
Like كان, ليس governs a nominal clause. Its subject, اسم ليس, is nominative; its predicate, خبر ليس, is accusative. In ordinary unvocalized writing the distinction may be invisible, but it appears in careful vocalization and in sound masculine plurals or duals: الموظفون ليسوا غائبين, with accusative/genitive ـين on the predicate.
هذا القرار ليس مناسبا الآن
hādhā l-qarāru laysa munāsiban l-ʾān
This decision is not appropriate now. (Formal neutral.)
المديران ليسا مقتنعين بالاقتراح
al-mudīrāni laysā muqtaniʿayni bil-iqtirāḥ
The two directors are not convinced by the proposal. (Formal.)
The predicate can also be a prepositional phrase, an adverbial expression, or a clause. Such predicates do not display a simple accusative ending: ليس في المكتب “is not in the office,” ليس عندي “I do not have,” and ليس من السهل أن... “it is not easy to....”
ليس في التقرير ما يثبت هذا الادعاء
laysa fī t-taqrīri mā yuthbitu hādhā l-iddiʿāʾ
There is nothing in the report that proves this claim. (Formal.)
ليس من السهل أن نتخذ قرارا بهذه السرعة
laysa mina s-sahli ʾan nattakhidha qarāran bihādhihi s-surʿa
It is not easy to make a decision this quickly. (Formal.)
Predicate بـ and frequent lexical frames
An extra, emphatic بـ may attach to the predicate after ليس: ليس ببعيد “is not far / is by no means far.” The following noun or adjective is genitive in form because of بـ, although the whole prepositional phrase fills the predicate role. This construction is especially common in formal prose and set phrases; it is not required in every negative sentence.
الحل ليس ببعيد إذا تعاون الفريقان
al-ḥallu laysa bibaʿīdin ʾidhā taʿāwana l-farīqān
A solution is not far off if the two teams cooperate. (Formal.)
Other high-frequency clusters include ليس بعد “not yet,” ليس فقط... بل أيضا “not only ... but also,” أليس كذلك؟ “isn't that so?”, and ليس هناك “there is/are not.”
المشكلة ليست في التكلفة فقط، بل في الوقت أيضا
al-mushkilatu laysat fī t-taklifati faqaṭ, bal fī l-waqti ʾayḍā
The problem is not only the cost but also the time. (Formal.)
أليس هذا هو الملف الذي طلبته؟
ʾalaysa hādhā huwa l-malaffa lladhī ṭalabtahu?
Isn't this the file you requested? (Formal neutral question.)
Common Mistakes
Giving ليس an imperfect form
❌ هو لا يليس متأخرا
Incorrect—ليس has no imperfect *يليس in contemporary MSA.
✅ هو ليس متأخرا
huwa laysa mutaʾakhkhiran
He is not late.
Using the wrong first-person stem
❌ أنا ليست مستعدا
Incorrect—first-person singular is لستُ, not ليست.
✅ أنا لست مستعدا لإعلان النتيجة
ʾanā lastu mustaʿiddan liʾiʿlāni n-natīja
I am not ready to announce the result.
Leaving a bare nominal predicate nominative
❌ الموظفون ليسوا غائبون
Incorrect in careful MSA—the bare predicate of ليس is accusative: غائبين.
✅ الموظفون ليسوا غائبين اليوم
al-muwaẓẓafūna laysū ghāʾibīna l-yawm
The employees are not absent today.
Using ليس for an explicitly past state
❌ ليس المكتب مفتوحا أمس
Incorrect with an explicitly past time in neutral MSA—use لم يكن.
✅ لم يكن المكتب مفتوحا أمس
lam yakuni l-maktabu maftūḥan ʾams
The office was not open yesterday.
Key Takeaways
- ليس is an irregular negative copula with perfect-shaped endings but normally present meaning.
- It has no imperfect, imperative, maṣdar, participles, or passive in this use.
- Its subject is nominative and its bare predicate accusative: ليس القرار مناسبا.
- Match person, gender, and number carefully: لست، لسنا، ليسا، ليسوا، لسن.
- Learn ليس بـ, ليس هناك, ليس بعد, and أليس كذلك؟ as distinct frequent frames.
Now practice Arabic
Reading grammar gets you part of the way. The exercises are where it sticks — free, no signup needed.
Start learning Arabic →Related Topics
- كان — beA2 — Reference the hollow verb كان across its full paradigm, copular and existential senses, predicate case, conditionals, and high-frequency collocations.
- ذهب — go and take إلى or لـ destination phrasesA2 — Use ذهب with its regular Form-I paradigm, destination and purpose frames, and frequent movement collocations.
- كان and Past Nominal SentencesA2 — Move Arabic nominal sentences into the past with inflected كان, a nominative subject, and an accusative nominal or adjectival predicate.
- The Arabic Verb SystemA1 — See how Arabic verb stems, agreement, mood, voice, and derived Forms work together in complete sentences.