A word is known as the smallest naming unit of the language. According to L. Bloomfield, word is a minimum free form. Close observation and comparison of words clearly shows that a great number of words have a composite nature and are made up of smaller units, each possessing sound-form and meaning. In other words, the term word denotes the basic unit of a given language resulting from the association of a particular meaning with a particular group of sounds capable of a grammatical employment is a word is therefore simultaneously a semantic, grammatical and phonological unit. The words of every language fall into classes which are called parts of speech. The problem of parts of speech is one of the controversial problems of modern linguistics. The theoretical side of this problem is the subject matter of the theoretical grammar. therefore we should base our comparison of system of parts of speech on the generally recognized (acknowledged) opinions of grammarians. In order to make easier to learn the language the grammarians usually divide the word-stock of the language into some subclasses called in linguists the parts of speech.