A category of word which typically denotes an entity of some kind.
In traditional grammar, a distinction is drawn between common nouns and proper nouns. Proper nouns are names of individual people (e.g. Chomsky), places (e.g. Colchester, Essex, England), dates (e.g. Tuesday, February, Easter), magazines (e.g. Cosmopolitan) etc., whereas common nouns (e.g. boy, table, syntax etc.) are nouns denoting general (non-individual) entities. Proper nouns have the semantic property of having unique reference. In some languages (e.g. some dialects of Brazilian Portuguese) proper nouns can be modified by a determiner, while in others, such as English, modification of a proper noun by a determiner is ungrammatical (cf. *the London).