A noun in the singular designates a single being, a single thing or a single idea. A noun in the plural designates several beings, several things or several ideas. In chat, there is only one animal. In chats, there are several. The number of the noun thus changes the quantity it expresses. Without this marking, the sentence does not give the same image of reality. The number of the noun also helps to correctly construct the article and the agreements with it, as in Definite articles and Indefinite articles.

Recognizing the number of the noun

Idea
A noun is singular when it designates a single being or a single object.
A noun is plural when it designates several beings or several objects.

The plural of nouns is most often formed with -s. One writes un livre and des livres, une table and des tables. In writing, this mark is visible; in speech, it is not pronounced in the majority of cases. The word therefore changes mainly in writing, while the article or determiner signals the number to the ear. This form applies to most Common Nouns and to many simple nouns. When the noun already ends with a silent consonant, the -s adds the plural mark without changing pronunciation. Words ending with -s, -x or -z also keep the same form in speech, but their plurality remains visible in the whole sentence.

Form the plural most often

Idea
We often form the plural by adding an s to the noun.
The plural marker is not always heard in speech.

Some nouns ending in -au, -eau or -eu take -x in the plural. One writes un bateau and des bateaux, un jeu and des jeux, un feu and des feux. This ending replaces the regular -s mark in these words. It concerns mainly a frequent group of simple nouns and a few Proper nouns used as common nouns in certain contexts. The singular keeps the full ending, then the plural adds -x without changing the word base. In speaking, the singular and plural often resemble one another, so the determiner becomes essential to show the number.

Special plurals of endings in u

Idea
Some nouns ending in au take x in the plural.
Some nouns ending in eau take x in the plural.
Some nouns ending in eu take x in the plural.

Several nouns in -al form their plural in -aux. One says un cheval and des chevaux, un journal and des journaux. The base changes slightly, but the meaning remains the same in the plural. Other nouns in -al keep the regular -s, such as des festivals or des récitals. For nouns in -ou, the general rule is -s: un clou, des clous. Some nouns take -x in the plural, such as des bijoux, des cailloux, des genoux, des hiboux, des joujoux and des poux. These forms must be learned with the noun itself, as is done for certain composed nouns and other particular plurals.

Irregular plurals of certain nouns

Idea
Several nouns ending in al become in aux in the plural.
Some nouns ending in ou take x in the plural.
Most nouns ending in ou take s in the plural.

A compound noun brings together two or more words to form a single idea. Its plural depends on the place and the nature of each element. In un porte-monnaie, only the second element keeps the idea of a thing; in the plural, one writes des porte-monnaie if the word remains invariable in common use, but some compounds take several marks, such as des grands-parents. When the compound contains a noun and an adjective, both can agree if the sense demands it. When it contains a verb or a preposition, part of the word often remains fixed. The plural of a Compound noun is read element by element, not merely as a single block ending in -s.

Plural of compound nouns

Idea
When the compound noun contains a noun and a noun the plural is often marked on both words.
When the compound noun contains a verb the verb often remains invariable.
When the compound noun contains a preposition the preposition remains invariable.

Some nouns keep the same form in the singular and the plural. The word does not change, even if the quantity changes. This is the case for several borrowings like des euros, des kilo in informal usages or for certain fixed-form words in everyday language. The number is then seen in the determiner or in the sense of the sentence. An invariable noun does not take -s, even when it refers to several realities. It functions like other fixed forms, close to Collective nouns when a single word can evoke an ensemble. The entire sentence must therefore carry the information of plurality.

Nouns that keep the same form

Idea
An invariable noun keeps the same form in the singular and plural.
Names of certain measures or materials are sometimes invariable.

The determiner often announces the noun’s number before one reads the end of the word. Le, la, un, une introduce a singular noun. Les and des introduce a plural noun. We say le jardin but les jardins, une fleur but des fleurs. With a plural noun, the determiner also becomes plural. This is particularly useful with nouns whose form does not change in speech. The determiner is placed before the noun and helps to identify its number, as in the structures studied with the Definite articles, Indefinite articles and Partitive article.

Identify the number using the determiner

Usage	Explanation
Singular indicator	We use a singular determiner to indicate that a single being or object is named.
Plural indicator	We use a plural determiner to indicate that several beings or objects are named.

The noun's number dictates the agreement of the words that accompany it. An adjective takes the singular with a singular noun and the plural with a plural noun: a small house, small houses. The verb also agrees with the nominal subject: the dog barks, the dogs bark. When the noun changes number, the forms related to that noun change with it. The agreement follows the sense of the noun phrase and is often visible in writing. This echoes the Agreement of the adjective and the Formation of the Adjective, where the ending depends on the noun it accompanies.

Agreements related to the number of the noun

Idea
The verb often takes the plural marking when the subject noun is plural.
The adjective agrees in number with the noun it accompanies.