Criteria of classifying words into parts of speech. Notional and functional classes of words.

Parts of speech – are classes of words united by a certain categorial meaning reflected in special grammatical markers.

Parts of speech occupy the central position in the language system because they enter two important domains of language at a time: lexicon and grammar.

The difficulty lies in the fact that though languages differ there should be worked out such a system that could embrace all classes of words of different languages having different characteristics.

The traditional classification is based exclusively upon the lexical (semantic) criterion.
Modern linguistic takes into account only formal (morphological) characteristics of words.

Here are several criteria of words belonging to a concrete part of speech.

1) The basis for the division of words into parts of speech is their real ties with material reality. The bulk of the vocabulary consists of words denoting substances: a table, a chair, etc. Then follows a big group of process-words: to write, to speak, etc. M eaning is that which unites these words. This general meaning is called lexico-grammatical or categorical meaning of a part of speech.

e. g. From the point of view of its lexical content a book, for example, is an object of reality surrounding us; from the point of view of its grammatical value it is a representative of a class of nouns characterized by a set of definite grammatical categories.

2) Lexico-grammatical meaning of a part of speech may have its expression in a word – lexico-grammatical morphemes (stem-building elements). Thus, nouns often have the morphemes -er, -ist, -ness, -ship, -ment; verbs contain the morphemes -ize, -ify, be-, en-, -en. Adjectives often end in the suffixes -ful, -less, -ish, -ous, -ive. So, a certain lexico-grammatical morpheme may indicate that a word belongs to a definite part of speech.

3) The third criterion according to which words are divided into parts of speech is the paradigm – a set of grammatical categories characteristic of this particular class of words.

e. g. Nouns in English have the categories of number and case. The categories of tense, voice, mood, etc. are typical of verbs. Adjectives possess the only category of degrees of comparison.

4) Speaking of functioning of parts of speech we should mention their combinability, or valency. This is the ability of the whole lexico-grammatical class of words to form combinations with words of other classes. This ability does not depend on lexical meanings of words.

5) Another important feature is the function of a part of speech in the sentence. Usually we assume that a noun occurs in the sentence in the function of a subject or an object, a verb functions as a predicate, an adjective – as an attribute, etc. Thus there are five basic principles on the basis of which scholars single out parts of speech.

Summarizing all this we can say that this classification is based on meaning, form and function. According to these three criteria words fall into notional (the noun, the adjective, the verb, the adverb, the pronoun, the numeral) and functional, or formal (the article, the preposition, the conjunction, the particle, the modal word, the interjection) parts of speech. The difference between them can be described roughly as follows: notional words denote things, properties, actions, etc. and other extralinguistic phenomena while functional words denote relations connecting notional words and have no direct tie with the extralinguistic world.