In linguistics, a noun class is a particular of nouns. A noun may belong to a given class because of the characteristic features of its referent, such as gender, animacy, shape, but such designations are often clearly conventional. Some authors use the term "grammatical gender" as a synonym of "noun class", but others consider these different concepts. Noun classes should not be confused with noun classifiers.
There are three main ways by which natural languages categorize nouns into noun classes:
according to similarities in their meaning (semantic criterion);
by grouping them with other nouns that have similar form (morphology);
through an arbitrary convention.
Usually, a combination of the three types of criteria is used, though one is more prevalent.
Noun classes form a system of grammatical agreement. A noun in a given class may require:
agreement affixes on adjectives, pronouns, numerals, etc. in the same noun phrase,
agreement affixes on the verb,
a special form of pronoun to replace the noun,
an affix on the noun,
a class-specific word in the noun phrase.
Modern English expresses noun classes through the third person singular personal pronouns he (male person), she (female person), and it (object, abstraction, or animal), and their other inflected forms. Countable and uncountable nouns are distinguished by the choice of many/much. The choice between the relative pronoun who (persons) and which (non-persons) may also be considered a form of agreement with a semantic noun class. A few nouns also exhibit vestigial noun classes, such as stewardess, where the suffix -ess added to steward denotes a female person. This type of noun affixation is not very frequent in English, but quite common in languages which have the true grammatical gender, including most of the Indo-European family, to which English belongs.
In languages without inflectional noun classes, nouns may still be extensively categorized by independent particles called noun classifiers.
Common criteria that define noun classes include:
animate vs.