The OED is a historical dictionary that records over 1000 years of the language's development. It aims to be a complete dictionary of the English language from

The OED is a historical dictionary that records over 1000 years of the language's development. It aims to be a complete dictionary of the English language from its origins to today. It frequently adds new entries and new examples of older words. I don't know that £100 per year is a reasonable price, but it's not an inexpensive endeavour to run; it employs many lexicographers. Most people don't need the full OED and should probably just buy one of the smaller Oxford dictionaries. The Concise Oxford English Dictionary is an excellent single-volume dictionary of modern English based on the Oxford Dictionary of English (which is not the same as the Oxford English Dictionary. The OED is a historical dictionary, while the ODE is a dictionary of contemporary English).