1. Classes of words

The words of language are divided into grammatically relevant sets of classes. The traditional grammatical classes of words are called "parts of speech".

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. The meaning is understood as the "categorical meaning of the part of speech (of a class).

The formal criterion provides for the exposition of the specific inflectional and derivational (word-building) features of all the lexemic subsets of a part of speech. It deals with word-building affixation pattern and word-form affixation (grammatical paradigm).

The functional criterion concerns the of words syntactic role (function) in the sentence typical of a part of speech and distribution combinability.

N. B. We can also speak about these categorial characterizations of words as meaning, form, function.

Examples of Different Classifications.

1. Traditional classification: words are divided into notional and functional:

- Notional: Nouns, Adjectives, Pronouns, Numerals, Verbs, Adverbs - these are the words of complete nominative value: in the utterance they fulfill self-dependent functions of naming and denoting things, phenomena, their substantial properties.

- Fuctional: Adlinks (they denote state, they are used only as complements, the have prefix a- (afraid, asleep)); Modal words (perhaps, of course, certainly, evidently, etc.); Prepositions; Conjunctions; Particles; Interjections; Articles; Response words (Yes/No) - these are the words of incomplete nominative value, but of absolutely essential relational (grammatical) value. In the utterance they serve as all sorts of mediators (посредник).

2. H. Sweet's classification:

H. Sweet divided all the words in 2 groups:

- declinables: (noun words - nouns, pronouns, pronumerals (cardinal numerals), infinitives, gerund): adjective words – adjectives, adjectival pronouns (possessive pronouns), adjectival numerals (ordinal numerals), participles; verbs).

- indeclinables: (adverbs, prepositions, conjunctions, interjections).

3. R. Quirk’s classification:

R Quirk divided all the words in 2 groups:

- open-class items (nouns, verbs, adjectives, adverbs). This class is "open" in the sense that it is indefinitely extendable. New items are constantly being created.

- closed-system items (articles - a, the, zero-article; demonstratives this, that, theses, those; pronouns; prepositions; conjunctions; interjections). The sets of items are closed in the sense that they cannot normally be extended by the creation of additional members.

4. Syntactico-distributional approach to classes of words:

American linguist Charles Fries invented the so-called "Corpus Data Linguistics". Charles Fries was a representative of the American Descriptive School. By the time of 50-s of the 20^th cen. American descriptivists had discovered the syntactic meaning - the meaning of a sentence which remains after the omission of lexical meaning of words. To demonstrate this they produced several nonsense sentences:

Woggles ugged diggles. Uggs woggled diggs. Woggs diggled uggles.

Smb. did smth. —> the syntactic meaning

The Syn.-dist. classification of words is based on the study of their combinability by means of substitution tests. For his materials Charles Fries chose tape-recorded spontaneous telephone conversations comprising about 250,000 word entries (50 hours of talk). The words isolated from this corpus are tested on three typical sentences, and used as substitution test frames:

Frame A: The concert was good (always). Frame B: The clerk remembered the tax (suddenly). Frame C: The team went there.

Charles Fries used the technique of substitution: all the words that can substitute for the word 'concert' with no change of structural syntactic meaning would belong to one class. As a result of this testing a standard model of 4 main syntactic positions of notional words was built up. These positions are those of the noun (N), verb (V), adjective (A) and adverb (D). Pronouns are included into the corresponding positional classes as their substitutes. 154 words remained undistributed into these 4 classes. Here belonged articles, auxiliaries, modal words, prepositions, conjunctions, etc., which belong to closed system items. Charles Fries divided them into 15 functional groups.