The Ministry of Higher and Secondary Specialized Education

CONCLUSION
Lexicology is a branch of linguistics. Lexicology deals with the vocabulary of a language and the properties of the words as the main units of language. And lexicography is one of its subdivisions, that is the theory and practice of compiling dictionaries.
The history of English lexicography is in its way one of the most remarkable developments in linguistics and therefore worthy of special definition. And the historical change in English lexicography is to create contemporary variation. The purpose of studying historical development of English lexicography purpose of is to trace the development of each meaning.
Dictionary is a book dealing with the individual words of a language (or certain specified class of them) so as to set forth their orthography, pronunciation, signification and use; their synonyms, derivation and history, or at least some of these facts, for convenience of reference the words are arranged in some stated order, now in most languages , alphabetical and in larger dictionaries the information given in illustrated by quotations from literature.
There are following types of dictionaries with definite focus on major aspects of the language:
Encyclopedic and Linguistic Dictionaries
Historical and Etymological Dictionaries Special Dictionaries
General Dictionaries
Different types of dictionaries differ in their aim, in the information they provide and their size.
Dictionaries do no tell their users how they ought, to speak and write the English language, but only how they can do so. And dictionary - users are to be told what is correct or incorrect in the language.

The most important problem of lexicology is the selection of words, the arrangement and definition of meaning and the arrangement of the vocabulary entry.

Lexicographical research has gone so far today, but much is lying ahead to be done and that needs more effort from the side of lexicographers to promote the lexicographic research further and we hope we'll have more types of dictionaries for everyday use and they will be under stable and helpful.