2.2. Morphemic level

The smallest bilateral unit in the hierarchy of language units is the morpheme defined as a minimal meaningful unit (L.Bloomfield).

There are three semantic types of morphemes:

• lexical (stem) morphemes, or the base: they carry the main lexical meaning of the word. Stems can be free, i.e. can stand alone as words or bound;

• derivational (word-building) morphemes: these serve to form new words;

• inflexional (form-building, grammatical) morphemes: they serve to form grammatical forms of words.

In its formal aspect, the morpheme is a bunch of instantiations, or morphs. When two or more morphological units are put together (e.g. stem + affix; two stems), either or both may undergo some modification (phonetic or graphic), thus forming an allomorph (a positional variant of a morpheme).

Allomorphs stand in complementary distribution to each other: if one variant of the morpheme is used in a certain position, it means that the other(s) cannot be used there.

Grammatical morphemes are scarce in English, which is an analytical language. Grammatical morphemes are wide-range abstractions. For example, -ed covers the whole of the subclass of verbs subject to this kind of form-building (regular verbs), whereas word-building morphemes cover a narrow range of words grouped into formal or semantic subclasses.

A grammatical morpheme is always a member of an opposition, i.e. opposed to some other morpheme that expresses the same general grammatical category, whereas word-building morphemes seldom form an opposition.

2.3. Lexical level

The word is the smallest naming unit of the language. The information contained in it is traditionally subdivided into denotational (referential) and categorial (significative) meaning (See the “semantic triangle” of Ogden-Richards).

The referential meaning reflects the symbolic connection established between a word and a certain fragment of the extralinguistic world. It is rendered by lexical morphemes, and is considered in the course of lexicology.

The conceptual meaning reflects the way we categorize the world in choosing a certain part of speech. It is mostly expressed by derivational morphemes, and is considered in the course of derivational morphology.

The word also possesses a purely grammatical meaning rendered by its inflexion (or lack of it - a zero inflexion). A word in a certain grammatical form, signaled by the inflexion, is called a word-form, or a grammeme. The system of grammatical forms makes the paradigm of the word.

2.4. Syntactic level

Syntactic units are: the word-group (word combination, phrase), the sentence, the member of the sentence.

Being included into a sentence, a word enters into relations with other words and acquires the status of a unit of speech - the member of the sentence.

The phrase is of an intermediary status between a word and a sentence.

The sentence is the main communicative unit of the language.

2.5. Textual level

Taking into account the achievements of recent decades, it is possible to add yet another, the highest level of the language description - that of the text. When a text is considered in its natural speech setting, it becomes discourse. In addition to text, discourse includes the process of production, of which the text is a product, and the process of interpretation, for which text is a resource, as well as social conditions of production and interpretation, the background knowledge of the speaker and hearer, their mutual knowledge of the situation in question, etc.