In short

Arabic has two regular ways of making a plural, and they are called “sound” - سالِم - because the singular survives inside them untouched. You add an ending and nothing else moves. One of them, ـونَ / ـينَ, is reserved for male human beings: مُعَلِّمٌ becomes مُعَلِّمونَ. The other one, ـات, replaces the feminine ة and is far more generous: مُعَلِّمَةٌ becomes مُعَلِّماتٌ, and so does سَيّارَةٌ, which is not a person at all. Between them these two endings cover a very large slice of the plurals you will need at A1, and they are the only plurals you can build yourself from the singular without looking anything up.

The reason to learn them together is that they behave the same way in one important respect and differ in another. Both have two endings covering three cases, not three endings - so each one collapses two cases into a single form - and it is the same pair in both: the accusative merges into the genitive. The masculine plural uses one form for the subject and another for everything else; the feminine plural uses one form for the subject and another for everything else too, and that second form carries a kasra, never a fatḥa. رَأَيْتُ الطّالِباتِ is correct and *رَأَيْتُ الطّالِباتَ is not, no matter how much your ear wants the fatḥa of an object.

The rule

1. Three kinds of plural, two of them regular. Arabic builds plurals in three ways: the two sound plurals of this lesson, which glue an ending onto the intact singular, and the broken plural, which reshapes the word from the inside (كِتابٌ → كُتُبٌ). Broken plurals are lesson 10 and they are the commonest kind, so do not conclude from this lesson that Arabic pluralizes regularly. Conclude the narrower and more useful thing: when a word takes a sound plural, you can produce it on the spot.

2. جَمْعُ المُذَكَّرِ السّالِم: ـونَ for the subject, ـينَ for everything else. Take the singular exactly as it stands, remove its case ending, and attach the plural ending:

• مُعَلِّمٌ → مُعَلِّمونَ (مَرْفوع) / مُعَلِّمينَ (مَنْصوب and مَجْرور)
• مُهَنْدِسٌ → مُهَنْدِسونَ / مُهَنْدِسينَ
• مُدَرِّسٌ → مُدَرِّسونَ / مُدَرِّسينَ
• مُسْلِمٌ → مُسْلِمونَ / مُسْلِمينَ

Three things about the ending itself. The و and the ي are long vowels, so the endings are two full syllables and impossible to miss. The ن always carries a fatḥa - مُعَلِّمونَ, never *مُعَلِّمونُ. And this plural takes no tanwīn at all, in any case: the indefinite مُعَلِّمونَ and the definite المُعَلِّمونَ differ only by the article. That ن is doing the job tanwīn does elsewhere, which is why the two never appear together.

3. Who is allowed this plural. Two groups only:

• nouns for male human beings: مُعَلِّمٌ، مُهَنْدِسٌ، مُوَظَّفٌ، لاعِبٌ، مُواطِنٌ
• adjectives and participles describing male human beings: مَشْغولونَ، مُجْتَهِدونَ، مِصْرِيّونَ

Nothing else, apart from one short closed list: a few words borrow the ending without belonging to the class - the tens عِشْرونَ، ثَلاثونَ and odd nouns such as سِنونَ “years” and أَهْلونَ “family” - and grammar books file them separately as مُلْحَق بِجَمْعِ المُذَكَّرِ السّالِم, “annexed to” the sound masculine plural. Outside that list a book, a car, a table, a dog and a mountain are permanently excluded, and so is every feminine noun. *كِتابونَ and *سَيّارونَ are not clumsy Arabic, they are impossible Arabic.

Note the direction of the restriction carefully: being a male human makes a noun eligible, not obliged. Plenty of male-human nouns have a broken plural instead - رَجُلٌ → رِجالٌ، وَلَدٌ → أَوْلادٌ، طالِبٌ → طُلّابٌ. The words that reliably take ـونَ are the derived ones: participles of the derived and quadriliteral verb patterns, active (مُعَلِّم، مُهَنْدِس) and passive (مُوَظَّف) alike - lesson 53 - and nisba adjectives in ـِيّ (lesson 21). If a male-human noun is short and basic, expect a broken plural and check it in the dictionary.

4. جَمْعُ المُؤَنَّثِ السّالِم: drop the ة, add ـات. The recipe is mechanical:

• مُعَلِّمَةٌ → مُعَلِّماتٌ
• طالِبَةٌ → طالِباتٌ
• سَيّارَةٌ → سَيّاراتٌ
• لُغَةٌ → لُغاتٌ

The ة never survives - you cannot write *مُعَلِّمَةاتٌ - because ـات already contains the feminine ت, now standing on its own two feet as a full consonant. Nouns that have no ة to begin with simply take ـات as it is: اِمْتِحانٌ → اِمْتِحاناتٌ، حَيَوانٌ → حَيَواناتٌ.

5. Its two endings, and the trap that defines this lesson. The feminine plural does take tanwīn, so it has four shapes in all - but only two vowels:

• مَرْفوع: طالِباتٌ / الطّالِباتُ - ḍamma, as you would expect
• مَنْصوب: طالِباتٍ / الطّالِباتِ - kasra
• مَجْرور: طالِباتٍ / الطّالِباتِ - kasra, the same form again

The sound feminine plural never takes a fatḥa. Where any ordinary noun would show مَنْصوب with a fatḥa, this plural shows a kasra instead and looks identical to the genitive:

• رَأَيْتُ الطّالِباتِ - I saw the students (object, and still a kasra)
• رَأَيْتُ طالِباتٍ - I saw some students
• سَأَلْتُ المُعَلِّماتِ - I asked the teachers

*رَأَيْتُ الطّالِباتَ is wrong. This is not an exception in the sense of an oddity to be memorised blindly; it belongs to a small family of endings called العَلاماتُ الفَرْعِيَّة, “substitute markers”, where a case is signalled by something other than its usual vowel. Lesson 40 collects them. For now, one sentence is enough: for ـات, accusative borrows the genitive’s kasra.

6. What the ـات plural covers. Much more than the masculine one:

• female human beings: مُعَلِّماتٌ، طالِباتٌ، مُهَنْدِساتٌ، مُمَرِّضاتٌ
• things and abstractions, whatever their gender: سَيّاراتٌ، ساعاتٌ، كَلِماتٌ، لُغاتٌ، جامِعاتٌ، مَطاراتٌ

Covering is not the same as claiming, though: a ة on the singular no more guarantees ـات than being male guarantees ـونَ, and many everyday feminine nouns take a broken plural instead - مَدينَةٌ → مُدُنٌ، مَدْرَسَةٌ → مَدارِسُ.

This is also the living, productive plural of the language: new words, technical terms and borrowings usually take ـات rather than being fitted to a broken pattern. When you coin or import a noun and need it plural, ـات is the safe bet.

7. Agreement: with people, everything goes plural. Lesson 8 taught that an adjective copies its noun in definiteness, case and gender. Add number to that list. When the plural refers to human beings, the adjective is plural too:

• المُعَلِّمونَ الجُدُدُ - the new teachers (جُدُدٌ is the broken plural of جَديدٌ)
• المُعَلِّماتُ الجَديداتُ - the new female teachers (a sound plural adjective)
• مُهَنْدِسونَ مِصْرِيّونَ - Egyptian engineers

The same applies to the predicate of a nominal sentence, which is مَرْفوع and normally indefinite: المُوَظَّفونَ مَشْغولونَ، الطّالِباتُ مُجْتَهِداتٌ. And the pronoun that stands for such a plural is هُمْ for men and هُنَّ for women (lesson 6).

Notice that the adjective does not have to use the same plural as its noun. المُعَلِّمونَ is a sound plural, الجُدُدُ is a broken one; each word takes whichever plural it happens to have. What must match is the grammatical number, not the shape.

One flag, because it will trip you otherwise: this plural-agreement rule holds for humans. A plural of non-human things takes a feminine singular adjective - سَيّاراتٌ كَثيرَةٌ, not *سَيّاراتٌ كَثيراتٌ. That rule is the whole of lesson 11; here just register that the two cases are different.

8. The ن disappears in an إِضافَة. When a sound masculine plural is the first term of a possessive construct, its ن drops:

• المُعَلِّمونَ → مُعَلِّمو الْمَدْرَسَةِ - the school’s teachers
• المُعَلِّمينَ → مُعَلِّمي الْمَدْرَسَةِ - (object or after a preposition)

Two spelling points. The و of مُعَلِّمو is followed by nothing - no silent alif, unlike verb forms such as كَتَبوا. And the first term of a construct takes no article, so *المُعَلِّمو is impossible. The feminine plural keeps its ت and its case vowel in the same position and drops only the tanwīn, as any first term does: مُعَلِّماتُ الْمَدْرَسَةِ. When and why any of this happens is lesson 20; recognise the shape now so it does not look like a typo.

9. Which of these endings will you actually hear? This matters more than it sounds. In ordinary formal speech, final short vowels are dropped before a pause - the pausal form - so most case endings are silent.

• ـونَ and ـينَ: audible. What separates the two cases here is the long vowel و / ي inside the ending, not a final short vowel, so the contrast between مُعَلِّمونَ and مُعَلِّمينَ survives in real speech - even in pause, where the fatḥa on the ن does itself drop. This is one of the very few places in MSA where you can hear case with your ears.
• ـاتُ / ـاتِ / ـاتٌ / ـاتٍ: not audible at the end of a phrase. What you hear is plain ـات. The vowel returns as soon as another word follows and the phrase runs on.

So: get the masculine endings right because people will hear them, and get the feminine endings right because you will need them the moment you write.

10. What this lesson deliberately leaves out. Broken plurals, which are the majority, are lesson 10. Agreement with non-human plurals is lesson 11. Two of something is neither singular nor plural in Arabic - the dual is lesson 12. And a family of nouns that refuses tanwīn altogether, among them names such as فاطِمَةُ and broken plurals such as مَدارِسُ, is lesson 41.

Forms & patterns

جَمْعُ المُذَكَّرِ السّالِم, with the singular alongside so you can see what the ending replaces:

جَمْعُ المُؤَنَّثِ السّالِم - note that the bottom two rows are identical:

Words that take the sound masculine plural:

Words that take the sound feminine plural - people first, then things:

Agreement, singular against plural:

The ن in and out of an إِضافَة (recognition only - lesson 20 owns the rule):

Examples

Common mistakes

• رَأَيْتُ الطّالِباتَ -> رَأَيْتُ الطّالِباتِ - the sound feminine plural never takes a fatḥa. Its accusative is spelled and pronounced exactly like its genitive.
• رَأَيْتُ طالِباتاً -> رَأَيْتُ طالِباتٍ - and the indefinite accusative is kasratān, so there is no silent alif to add either. The ـات ending simply has no fatḥa form.
• رَأَيْتُ الْمُعَلِّمونَ -> رَأَيْتُ الْمُعَلِّمينَ - ـونَ is only for the subject. The object, and anything after a preposition, takes ـينَ.
• مَعَ الْمُهَنْدِسونَ -> مَعَ الْمُهَنْدِسينَ - same rule seen from the other side: a preposition puts its noun in the مَجْرور, and for this plural that is ـينَ.
• مُعَلِّمينٌ -> مُعَلِّمينَ - the sound masculine plural takes no tanwīn in any case. Only الـ marks it definite; without الـ it is already indefinite.
• مُعَلِّمونُ -> مُعَلِّمونَ - the ن of this plural always carries a fatḥa, whichever case the word is in.
• مُعَلِّمَةونَ -> مُعَلِّماتٌ - a feminine noun can never take ـونَ. Drop the ة and add ـات; that is the only regular plural it has.
• كِتابونَ / سَيّارونَ -> كُتُبٌ / سَيّاراتٌ - ـونَ is for male humans only. A book takes a broken plural (lesson 10), a car takes ـات.
• رَجُلونَ -> رِجالٌ - a male human, yes, but this particular noun has a broken plural. Eligibility is not obligation; learn each noun’s plural with the noun.
• المُعَلِّمونَ الْجَديدُ -> المُعَلِّمونَ الْجُدُدُ - an adjective describing a human plural must itself be plural, even when its plural is of the other kind.
• المُعَلِّماتُ الْجَديدَةُ -> المُعَلِّماتُ الْجَديداتُ - feminine singular agreement is for non-human plurals (lesson 11). Women are human, so the adjective is plural.
• المُعَلِّمونَ الْمَدْرَسَةِ -> مُعَلِّمو الْمَدْرَسَةِ - in an إِضافَة the ن drops and the first term loses its article.

Tips

• Learn the masculine plural as a pair of sounds, not as a table: ـونَ for the doer, ـينَ for everyone else. Say a dozen nouns aloud both ways until the swap is automatic.
• Store every new noun with its plural, the way you already store it with its tanwīn: مُهَنْدِسٌ - مُهَنْدِسونَ، سَيّارَةٌ - سَيّاراتٌ. Guessing costs more than memorising.
• The single fact worth over-learning from this lesson is that ـات has no fatḥa. Write out رَأَيْتُ الطّالِباتِ a few times; the error it prevents is the one examiners look for.
• A quick eligibility test for ـونَ: could you point at the group and say “these men”? If not - if it is women, objects, animals or ideas - the ending is out of the question.
• ـات is your fallback. When you genuinely do not know a plural and the noun is feminine or inanimate, ـات is more often right than any broken pattern you might invent.
• Do not try to hear the feminine case endings in speech; they vanish before a pause. Treat them as something you produce in writing and in careful reading.
• Ignore for now what happens when these plurals meet a number, and what a group of two takes - numbers are lesson 26 and the dual is lesson 12.
• When you meet مُعَلِّمو or مُهَنْدِسي in a text and the ن seems to be missing, look at the next word: it will be the second half of an إِضافَة.