Nouns, verbs, adjectives, and adverbs form open classes – word classes that readily accept new members, such as the noun "celebutante" (a celebrity who frequents the fashion circles), and other similar relatively new words. The others are considered to be closed classes. For example, it is rare for a new pronoun to enter the language. Determiners, traditionally classified along with adjectives, have not always been regarded as a separate part of speech. Interjections are another word class, but these are not described here as they do not form part of the clause and sentence structure of the language.