A sound plural is a suffix which is added to the end of the word in order to indicate the plural. The suffixes reflect gender and case as well. First we will deal with masculine sound plurals and then with feminine ones.
Masculine sound plurals have the suffix ونَ attached to them in order to indicate the plural in the nominative case. In the genitive and accusative cases the ending is ينَ For example, the plural of مدير is مديرونَ in the nominative case and مديرينَ if the word is in the accusative or genitive cases. Look at the two sentences below.
The directors are in their office. المديرونَ في مكتبِهِم
This memo is from the directors. هذه المذكرة من المديرينَ
In the first sentence, the plural of ,المدير is written in the nominative case to indicate that it is the subject, whereas in the second sentence we see the genitive case because of the preposition. Remember that the accusative form will be the same as the genitive form.
Many students think that the fatha which is written over the ن in these plurals (ونَ , ينَ) is itself a case ending. The fatha is not a case ending. It is just a part of the plural and is really only functional as a helping vowel. Indeed, the fatha is usually dropped in pausal form. The و and the ي, in addition to being integral parts of the plural, are the indicators of the case of the word.
Sound plurals are also used with many adjectives. For example مُمتاز takes a sound plural ending. So do almost all nisba adjectives. For example, we wish to say that “The Egyptian directors are superb.” In Arabic we get:
المديرونَ المصريّونَ ممتازونَ.
المديرونَ is nominative because it is the subject of the equational sentence. المصريّونَ agrees with the word it modifies in every way. It is definite, it is nominative, and it is plural. Also NOTE THE SPELLING OF المصريّونَ. Many students seem to think the يّ of the nisba adjective disappears in the plural. This is not the case. The يّ of the nisba adjective never disappears when the sound plural suffix is added. This is true even when the sound plural suffix is in the accusative/genitive case. المصريّونَ when written in the accusative or genitive is المصريّينَ So do not ever drop the يّ of the nisba adjective when you make a sound plural.
Finally, note that ممتازونَ is plural and nominative as it is the predicate of an equational sentence with a masculine plural subject.
Masculine sound plurals are only used for words which refer to male human beings. In other words, a non-human noun such as بيت can never have a masculine sound plural. However, not all masculine nouns which do refer to human beings have sound plurals. For example, the plural of مدرس is مدرسون but the plural of أستاذ is اساتِذة . Basically, you never can be sure what the plural of any word is in Arabic (though you can learn to make educated guesses), so you must learn the plural of each word when you learn its singular form. With respect to masculine sound plurals, however, you may generally assume that any active or passive participles of derived verbs will take a masculine sound plural if they refer to male human beings. If this last sentence is Greek to you, do not worry; you will see what I mean in later chapters.
In order to form a feminine sound plural, we drop the ‘o from the word and then add the suffix اتٌ. For example, the plural of مُدَرِّسة is مُدَرِّساتٌ For the genitive and accusative cases we use only the two kasras. So the accusative or genitive case form of the word in question is مُدَرِّساتٍ If we make a feminine plural definite, it loses the nunation. Do not forget that, just like the masculine, the feminine sound plural uses the same case markers in the accusative as it does in the genitive. اتٍ for the feminine and ين for the masculine.
Feminine sound plurals are used for almost all nouns which refer to female human beings, for many other feminine nouns which do not refer to human beings, and for some masculine nouns which also do not refer to human beings. In addition, adjectives which are made feminine with the addition of a ة will also take feminine sound plurals when the need arises.
Here are some examples. طاوِلة is a non-human feminine noun. It takes a regular feminine sound plural طاولاتٌ. مطار (airport) is a masculine non-human noun. Its plural is مطاراتٌ “. Thus, although مطارis masculine in the singular, it takes a feminine sound plural. You must try to learn the plural of each word as you learn its singular.
Most adjectives are made feminine by adding a ة. For example جديد becomes جديدة and عراقيّ becomes عراقية ّ. All of these adjectives will take a feminine sound plural. So in order to say that the Iraqi (f) teachers are in their office we say المدرساتُ العراقياتُ في مكتبِهِنَّ .
One final note. Look out for nouns which are feminine and end in ة but do not have feminine sound plurals. Instead they have broken plurals. There are many of them. For example, the plural of جريدة (newspaper) is جَرائد and the plural of مدرسة (school) is مَدارِس
You cannot always tell by looking at a word what its plural will be. You will need to learn the plurals of new words as you learn their singulars – as I have already said.