1. Lexicology as a branch of linguistics. Lexical units

the selection of lexical units for inclusion (The choice of lexical units for inclusion in the prospective dictionary is one of the first problems the lexicographer faces.
First of all the type of lexical units to be chosen for inclusion is to be decided upon. Then the number of items to be recorded must be determined. Then there is the basic problem of what to select and what to leave out in the dictionary. Which form of the language, spoken or written or both, is the dictionary to reflect? Should the dictionary contain obsolete and archaic units, technical terms, dialectisms, colloquialisms, and so forth?
There is no general reply to any of these questions. The choice among the different possible answers depends upon the type to which the dictionary will belong, the aim the compilers pursue, the prospective user of the dictionary, its size, the linguistic conceptions of the dictionary-makers and some other considerations) 2) their arrangement, 3) the setting of the entries (Since different types of dictionaries differ in their aim, in the information they provide, in their size, etc., they of necessity differ in the structure and content of the entry. The most complicated type of entry is that found in explanatory dictionaries. In explanatory dictionaries of the synchronic type the entry usually presents the following data: accepted spelling and pronunciation; grammatical characteristics including the indication of the part of speech of each entry word, the transitivity and intransitivity of verbs and irregular grammatical forms; definitions of meanings; modern currency; illustrative examples; derivatives; phraseology; etymology; sometimes also synonyms and antonyms),4) the selection and arrangement (grouping) of word-meanings, 5) the definition of meanings, 6) illustrative material, 7) supplementary material.
When the selection of the dictionary entries, the contents and structure of the entries, their order of arrangement etc. are decided upon, the lexicographer is to settle upon this or that structure of the dictionary. In spite of the great variety of linguistic dictionaries their composition has many features in common. Nearly all of them may be roughly divided into three unequal parts.
Apart from the dictionary proper, that make up the bulk of the wordbook, every reference book contains some separate sections which are to help the user in handling it — an Introduction and Guide to the use’ of the dictionary. This prefatory matter usually explains all the peculiarities of the word-book, it also contains a key to pronunciation, the list of abbreviations used and the like.
It is very important that the user of a dictionary should read this prefatory matter for this will enable him to know what is to be found in the word-book and what is not, will help him locate words quickly and easily, and derive the full amount of information the dictionary affords.
Appended to the dictionary proper there is some supplementary material valuable for language learners and language teachers. This material may be divided into one of linguistic nature, pertaining to vocabulary, its development and use, and the other pertaining to matters distinctly encyclopaedic. In explanatory dictionaries the appendixes of the first kind usually include addenda or/and various word-lists: geographical names, foreign words and expressions, forenames, etc., record new meanings of words already entered and words that have come into existence since the compilation of the word-book. The educational material may include a list of colleges and universities, special signs and symbols used in various branches of science, tables of weights and measures, etc.
In translation dictionaries supplementary material is in some respects different from that in explanatory dictionaries, e.g. the Russian-English dictionary referred to above does not only include a list of geographical names, standard abbreviations pertaining to the public, political, economic and industrial life, but also contains the rules of English and Russian pronunciation as well as brief outlines of English and Russian grammar.