An entity is specified as indefinite when it refers to a non-particularized individual of the species denoted by the noun. (http://languagelink.let.uu.nl/tds/onto/LinguisticOntology.owl#indefinite) Indefinite noun phrases are used to refer to entities which are not specific and identifiable in a given context. (http://en.wikipedia.org/wiki/Definiteness 20.11.06)