1)The morphological system of language reveals its properties through the morphemic structure of words. It follows from this that morphology as a part of grammatical theory faces the two segmental units: the morpheme and the word. But the morpheme is not identified otherwise than part of the word; the functions of the morpheme are effected only as the corresponding constituent functions of the word as a whole.

For instance, the form of the verbal past tense is built up by means of the dental grammatical suffix train-ED, publish-ED,meditate-ED.

Thus, in studying the morpheme we actually study the word in the necessary details of its composition and functions.

It is difficult to give a rigorous and at the same time universal definition of the word. This difficulty is explained by the fact that the word is an extremely complex and many-sided phenomenon. Within the framework of different linguistic trends and theories the word is defined as the minimal potential component of the sentence, the articulate sound-symbol, the grammatically arranged combination of sound with meaning, the meaningfully integral and immediately identifiable lingual unit, the uninterrupted string of morphemes.

these difficulties compel some linguists to refrain from accepting the word as the basic element of language.

For example Bloomfield recognized not the word and the sentence, but the morpheme and the morpheme as the basic categories of linguistic description, because these units are the easiest to be isolated in the continual text due to their physically minimal meaningful element. Accordingly only two segmental levels were originally identified in language by descriptive scholars – the phonemic and the morphemic level, later on a third one was added to these – the level of constructions. That is the level of morphemic combinations.

As for the criterion according to which the word is identified as a minimal sign capable of functioning alone, it is relevant for the bulk of functional words which cannot be used independently even in elliptical responses. In spite of these shown difficulties however there remains the unquestionable fact that each speaker has at his disposal a ready stock of naming units by which he can build up an infinite number of utterances reflecting the ever changing situations of reality.

This circumstance urges us to seek the identification of the word as a lingual unit-type on other lines than the strictly operational definition . in fact we do find the classification of the problem in taking into consideration the difference between the two sets of lingual phenomena: one the one hand polar phenomena, on the other hand intermediary phenomena.

Within a complex system of interrelated elements, polar phenomena are the most clearly identifiable, they stand to one another in an utterly unambiguous opposition. Intermediary phenomena are located in the system in between the phenomena making up a gradation of transitions or the so-called continuum’. By some of their properties intermediary phenomena are similar or near to one of the corresponding poles, while by other properties they are similar to the other, opposing role. The analysis of the intermediary phenomena from the point of view of their relation to the polar phenomena reveal their own status in the system. At the same time this kind of analysis helps evaluate the definitions of the polar phenomena between which a continuum is established.

So, the morpheme is meaningful segmental component of the word; the morpheme is formed by phonemes.; as a meaningful component of the word it is elementary.

In traditional grammar the study of the morphemic structure of the word was conducted in the light of the two basic criteria – positional ( the location of the marginal morphemes in relation to the central ones) , and semantic or functional ( the correlative contribution of the morphemes to the general meaning of the word.)))

The combination of these two criteria in an integral description has led to the rational classification of morphemes that is widely used both in research linguistic work and in practical lingual tuition.

2) Grammatical category and its characteristic features.

M.Y. Blokh defines the grammatical category as "a system of expressing a generalized grammatical meaning by means of paradigmatic correlation of grammatical forms". It’s a unity of form & mean-g. 1)The general notion on which a gram. category grounds is gram. mean-g. 2)The forms united into a grammatical category possess a common general meaning that gives a name to the category and each form possesses its own specific meaning that presents a specification of the general meaning and differentiates the form from the other form/forms within the category. The forms lives - lived - will live are united on the basis of the common general grammatical meaning of tense and constitute the grammatical category of tense. Within this category each form has its own specific meaning of tense: present, past and future. 3) gram. categories don’t nominate objects or units of lang., instead they express relations between lang. units. The grammatical category of tense presents a specific lingual expression of objective time, the grammatical category of case presents various relations between the action and its participants, the grammatical category of number in nouns reflects the quantitative relations between homogeneous objects of reality, the grammatical category of mood presents the relations between the action and reality as they are presented by the speaker etc. Such grammatical categories may also be called inherent (неотъемлемый, присущий). 4) Conceptual (понятийные) grammatical categories are universal, they exist in most of the languages though their volume and their scope may vary considerably in various languages. Gram. cat-s represent lang. realization of universal cat-s of human thinking. That’s why gram. cat-s typical of a particular lang. are unique. The grammatical category of number is the most universal grammatical category, all speech communities have linguistic means of encoding number, though these means differ greatly in different languages. 5) A grammatical category is constituted on the basis of contrastive grammatical forms which share a certain grammatical meaning correlated to some general concept (time, number) and differ in more concrete meanings within the scope of the same concept. Such contrastive grammatical forms are called oppositions and all grammatical categories are based on oppositions. The method of oppositional analysis was introduced by Trubetskoy . Now the method of oppositional analysis is widely used in lexicology and grammar.

3) Parts of speech and different principles of their classification.

The general definition of a part of speech: it is a lexical-grammatical word class which is characterized by a general abstract grammatical meaning, expressed in certain grammatical markers. Within a part of speech similar grammatical features are common to all words belonging to this class.

A part of speech is a mixed lexical-grammatical phenomenon, because:

1) Words are characterized by individual lexical meanings. 2) Each generalized class of words (noun/verb/adj., etc) has a unifying abstract gram. meaning, for ex.: noun – substance, verb – process, adjective – quality of substance, adverb – quality of process. 3) Some parts of speech are capable of representing gram. meaning in a set of formal exponents; for ex.: the plural of nouns is expressed with suffix –s (this feature is not universal in all languages).

PS are distinguished from one another by the number of wds in each class. The greatest number of wds is found in the noun & verb. The N&V correspond to the subj.&pred. of the sent., they’re usually the center of predication.

Modern classification of parts of speech is traced back to ancient Greek. Later this classification was applied to Latin and thus it found its way in modern languages. The present day classification of parts of speech is severely criticized, when it’s applied to languages the structure of which is different to the structure of the Latin language. So the criticism is easily justified. On the other hand the traditional division of words into parts of speech seems quiet natural and easy to understand & remember from the logical point of view. So it’s not the classification itself that is wrong but it must be the principles of classification that should be criticized and reviewed.

Classifying a lang. from the view point of PS, there are the following principles:

1. Semantic: the general mean-g of a PS doesn’t coincide with a lex. or gram.mean-g of every individual word, but it’s closely connected with it. Thus the gen. mean-g of a PS is neither lex. nor gram., but it’s to be called lexical-grammatical. Ex. nouns are characterized by substantivity, verbs- actions & states, which together mean processes, adj-s- attributes of substances, etc.

2. Morphological: it has 2 aspects: a) deals with morphol. categories (each PS possesses certain morphol. cat-s which are not found in other PS): ex. nouns- case & number , adj.- comparison, verbs- 7 categories. This aspect is more important.b) the use of form-build. affixes (deriv. affixes sometimes can be found within this or that PS only): ex. nouns- -ment, -ion, -ness. But deriv. affixes may be highly confusing: ex. –ly: friendly(adj), daily(noun), kindly(adv.), possibly (modal wd)

3. Syntactic: a) the role of a wd in a sent. (dif. synt. Functions are typical of dif. PS); b) the combinability of wds/ the syntactical distribution (распределение): ex. noun can combine with prepositions, articles, adj-s, other nouns, verbs.

4. Functional: PS- a field that has a core & a periphery.