We often hear people refer to any alphabetically organized book of defined words (especially if they think it supports their position) as “the dictionary.” This hurts our feelings, for it makes it sound as though there was only one such book, and all the lexicographers out there, toiling away for years on end to craft careful explanations of hundreds of thousands of words, are all just repurposing some master list, perhaps by changing the font, or putting a new cover on an existing book.
A great number of English dictionaries have been published since Robert Cawdrey first released his A Table Alphabeticall in 1604. How many? Well, it is not possible to give an exact number, but in Arthur Kennedy’s 1927 Bibliography of Writings on the English Language he lists well over 500 published between 1604 and 1922. Almost all of these are general monolingual works, and there are thousands of other dictionaries that deal with slang, learner’s English, and specialized fields.
Every one of these dictionaries is different from the others. They differ in scope and ambition, in terms of the geography and register of the language they cover, and in terms of accuracy.