The distribution of word units into classes described in grammars as parts of speech is one of most widely discussed problems in English. So far there remains a number of unsolved problems: 1) the cardinal specifies of a part of speech foundation; 2) the number of parts of speech; 3) the role of syntax in morphological representation of the part of speech.

    As far as it is concerned the very term parts of speech is subjected to more criticism as it contradicted the established division into language and speech. Its morphology modifies the language paradigmatic foundation, speech reveals its dynamic nature in syntagmatics. The parts of speech as a phenomenon of morphology offered just a paradigmatic structures. In this respect the term “parts of speech” somewhat contradicts itself. Though in a language like English where the hypnosis of morphological forms is taken away as to their inflexion stock scarcity a word unit may be a noun, verb, adjective, adverb, etc. without changing its morphological structure.

        He has no equal (n)

              On equal terms (adj)

We equal the rights (v)

Dress them equal (adv)

    The position of the word in the sentence affects its morphological reference and permits of revealing the paradigm of the verb, noun, adverb, etc. The very reference of a word to a part of speech turns out to be the function of its syntactic employment. The function comes a secondary phenomenon, the syntactic position being primary.

    Grammarians long ago recognized the fact that there must be different kinds of words, according to the positions they can fill and the functions they can perform in various structures; the name “parts of speech” was given to these various types of words.     An adequate definition of parts of speech must naturally proceed from a set of criteria that can be consistently applied to all lexical units of a given language. We cannot, for instance, use only “lexical meaning” as the basis for the definition of some word-classes, “function in the sentence” for others, and “formal characteristics” for still others.

    Parts of speech must be defined as lexico-grammatical word-classes which differ in their grammatical meaning and forms, word-making devices and functions in the sentence. In modern linguistics, parts of speech are discriminated on the basis of the three criteria: “semantic”, “formal”, “functional”. The semantic criterion presupposes the evaluation of the generalized meaning, which is characteristic of all the subsets of words constituting a given part of speech. This meaning is understood as the “categorical meaning of the part of speech”. The formal criterion provides for the exposition of the specific inflexional and derivational (word-building) features of all the lexemic subsets of a part of speech. The functional criterion concerns the syntactic role of words in the sentence typical of a part of speech.

    2. Functional and notional words

In accord with the traditional criteria of meaning, form and function, words on the upper level of classification are divided into notional and functional.

    In English to the notional parts of speech are usually referred the noun, the adjective, the numeral, the pronoun, the verb, the adverb. The notional parts of speech are the words of complete nominative value; in the utterance they fulfil self-dependent functions of naming and denoting things, phenomena, their substantial properties. Opposed to the notional parts of speech are the functional words which are words of incomplete nominative value, but of absolutely essential grammatical value. In the utterance they serve as all sorts of mediators. They are: the article, the preposition, the conjunction, the particle, the modal word, the interjection.

    It must be emphasized that the difference between notional words and functional ones is often not so much a matter of form as of content. In semantic term, function words are known to be weak and very general. Considered in form, they sometimes coincide with notional parts of speech. Compare the verb get, go, grow in the following patterns: to get a letter, to go home, to go bad, to grow potatoes to grow dark.

              The boy says that the guests did arrive.