Dictionary is a book that lists words in alphabetical order. It is extremely useful to people who wish to learn any language. It helps to know the spelling, usage , meaning and pronunciation of a word. It also helps to improve one's vocabulary. The first dictionary in English was written by samuel Johnson. He had to face many hardships to complete his work. Some dictionaries give the meaning of the word we search in the same language while some dictionaries give the equivalent word and meaning in a different language. To improve one's knowledge in a language, a dictionary is absolutely essential. How is it possible to know the meaning of one unknown word in the ocean of words without a dictionary ? Nowadays dictionaries are even available online and this makes our work a lot easier.