As a historical dictionary, the Oxford English Dictionary explains words by showing their development rather than merely their present-day usages.
Therefore, it shows definitions in the order that the sense of the word began being used, including word meanings which are no longer used. Each definition is shown with numerous short usage quotations; in each case, the first quotation shows the first recorded instance of the word that the editors are aware of and, in the case of words and senses no longer in current usage, the last quotation is the last known recorded usage. This allows the reader to get an approximate sense of the time period that a particular word has been in use, and additional quotations help the reader to ascertain information about how the word is used in context, beyond any explanation that the dictionary editors can provide.
The format of the OED's entries has influenced numerous other historical lexicography projects. The forerunners to the OED, such as the early volumes of the Deutsches Wörterbuch, had initially provided few quotations from a limited number of sources, whereas the OED editors preferred larger groups of quite short quotations from a wide selection of authors and publications. This influenced later volumes of this and other lexicographical works.