The very moment I think of a dictionary the name that strikes my mind is Oxford. I started using Oxford dictionary from the age of 8 and till date it is the best dictionary I have ever come across.
In the beginning I used a concise dictionary and later moved on to this advanced learner’s dictionary.
It gives the meanings of words in an easy to understand way along with an example to understand it better. It also tells the parts of speech of each word listed in it along with phonetics to make the readers better understand the way in which the word is supposed to be pronounced. It is published by the Oxford University Press. You can undoubtedly buy this book.