1. Positional mobility within the sentence;

2. Morphological uninterruptability;

3. Semantic intergrity.

Types of words

Semantically: monosemantic, polysemantic

Stylistically: stylistically marked, stylistically neutral.

Syntactically: notional, functional.

Etymologically: native, borrowed, international.

Emotionally: colored, neutral.

According to the nature and the number of morphemes constituting a word there are different structural types of words in English simple, derived, compound, compound-derived.

Simple words consist of one root morpheme and an inflexion (in many cases the inflexion is zero), e.g. «seldom», «chairs», «longer», «asked».

Derived words consist of one root morpheme, one or several affixes and an inflexion, e.g. «derestricted», «unemployed».

Compound words consist of two or more root morphemes and an inflexion, e.g. «baby-moons», «wait-and-see (policy)».

Compound-derived words consist of two or more root morphemes, one or more affixes and an inflexion, e.g. «middle-of-the-roaders», «job-hopper».

When speaking about the structure of words stems also should be mentioned. The stem is the part of the word, which remains unchanged throughout the paradigm of the word,

e.g. the stem «hop» can be found in the words: «hop», «hops», «hopped», «hopping». The stem «hippie»can be found in the words: «hippie», «hippies», «hippie’s», and «hippies’». The stem «job-hop» can be found in the words: «job-hop», «job-hops», «job-hopped», and «job-hopping».

So stems, the same as words, can be simple, derived, compound and compound-derived.

4 The notion of lexical system

Lexical units are 2-facet elements possessing form and meaning. They constitute the system.

The term system denotes not merely the sum total of English words; it denotes a set of elements associated and functioning together according to certain laws. It is a coherent homogeneous whole, constituted by interdependent elements of the same order related in certain specific ways.

The vocabulary of a language is moreover an adaptive system constantly adjusting itself to the changing requirements and conditions of human communications and cultural surroundings. Some new words appear, some word become obsolete and drop out of the language.

Lexicology studies this whole by determining the properties of its elements and the different relationships of contrast and similarity existing between them within a language, as well as the ways in which they are influenced by extra-linguistic reality.

The extra-linguistic relationships refer to the connections of words with the elements of objective reality they serve to denote, and their dependence on the social, mental and cultural development of the language community.

Academician V.V. Vinogradov has called it the lexico-semantic system. The interdependence in this system results from a complex interaction of words in their lexical meanings and the grammatical features of the language.

V.V. Vinogradov includes in this term both the sum total of words and expressions and the derivational and functional patterns of word forms and word-groups, semantic groupings and relationships between words.

All elements of the system have certain types of relationships between them. They are: syntagmatic, paradigmatic.

S relations define the meaning of the word possesses when it is used in combination with other words in the flow of speech,

e.g. He got a letter. He got tired. He got to London.

Paradigmatic relations exist between individual lexical items which make up one of the subgroups of vocabulary items.

S.R. are based on the linear character of speech, they are studied by means of contextual, valency, distributional and some other types of analysis.

P.R. are based on the interdependence of words within the voc-ry (synonymy, hyponymy, antonymy).

He got a letter.

I received a note.

She obtained an epistle.

So, the course of English L. may be subdivided into two main parts: the treatment of the English word as a structure, the treatment of the Engl. vocabulary as a system.