noun

A noun is a word that names a person, place, thing, or idea. Nouns function as the main reference in noun phrases and serve as the syntactic backbone of sentences, where they can act as subjects, objects, or complements.

Nouns are commonly categorized in several ways. Common nouns name general items (city, river); proper nouns name specific items and are capitalized (London, Nile). They can be countable or uncountable (mass) nouns describing quantities that can be counted (apple, idea) or substances that are not easily counted on their own (water, sand). Abstract nouns refer to ideas or states (freedom, happiness). Concrete nouns refer to things perceived by the senses (flower, thunder). Collective nouns refer to a group (team, committee).

Noun phrases are built around a noun head and can include determiners (the, this, my), adjectives (red, large), and complements. Nouns can take plural forms (cats, ideas) and possessive forms (cat's toy, children's books).

In English, nouns show limited morphology compared with some other languages: plurality is usually marked, and possessive form is typically marked by 's or s' for plural nouns ending in s. Many languages assign gender or case to nouns, affecting agreement with verbs or adjectives.

Choosing the appropriate noun type and form affects meaning and grammaticality. Proper nouns require capitalization; common nouns do not. Nouns are central to naming and categorizing elements of reality and thought.