Part of speech
A part of speech is a grammatical category of words in a language. In English, the eight parts of speech are the noun, the verb, the adjective, the adverb, the pronoun, the preposition, the conjunction, and the interjection. Other languages have more or fewer parts of speech. For example, in Mandarin Chinese, the two parts of speech are content words or full words, having concrete meanings; and function words or empty words, indicating grammatical relationships.
Parts of speech can be open classes, which readily accept new members, and closed classes, which do not. For example, nouns are an open class, since most languages allow new nouns to be coined with ease, while prepositions are a closed class.