R. S. Ginzburg, S. S. Khidekel, G. Y. Knyazeva, A. A. Sankin a course in modern english

§ 3. Explanatory Dictionaries

Out of the great abundance of linguistic dictionaries of the English language a large group is made up of the so-called explanatory dictionaries,¹ big and small, compiled in English-speaking countries. These dictionaries provide information on all aspects of the lexical units entered: graphical, phonetical, grammatical, semantic, stylistic, etymological, etc.
Most of these dictionaries deal with the form, usage and meaning of lexical units in Modern English, regarding it as a stabilised system and taking no account of its past development. They are synchronic in their presentation of words as distinct from diachronic, those concerned with the development of words occurring within the written history of the language. For instance, the New English Dictionary on Historical Principles commonly abbreviated in NED and its abridgement The Shorter Oxford Dictionary on Historical Principles (SOD) coyer the history of the English vocabulary from the days of King Alfred down to the present time; they are diachronic, whereas another abridgement of the NED — the Concise Oxford Dictionary of Current English (COD) as well as H. C. Wyld's Universal Dictionary of the English Language are synchronic. Other series of authoritative synchronic explanatory dictionaries are Webster dictionaries, the Funk and Wagnalls (or Standard) dictionaries and the Century dictionaries.
It should be noted that brief remarks of historical and etymological nature inserted in dictionaries like the COD do not make them diachronic. Moreover, dictionaries of a separate historical period, such as Anglo-Saxon Dictionary by J. Bosworth and T. N. Toller, Stratmann's Middle English Dictionary by H. Bradley, which are sometimes called historical, cannot be strictly speaking referred to diachronic wordbooks. They do not trace the evolution of the language, but study a synchronic cross-section, i.e. the words of a historical period are regarded from a synchronic angle.