Dictionaries have existed for hundreds of years. They are very helpful for travellers, language learners and teachers. In fact the study of word meanings and dictionary-making and dictionary analysis has given plenty of insights into language in general and vocabulary in particular. Over the past thirty years or so, advances in computer technology have revolutionised the field of lexical studies. The advent of computerised language corpora (i.e. principled collections of running text) makes it possible to retrieve and analyse lexical information in systematic ways. Now linguists and lexicographers are able to answer the following questions. (a) What types of dictionary entry can be found in a dictionary? (b) How do we account for polysemy in dictionaries? How do we discern different word senses? (c) What kinds of examples are most effective when trying to show how a word is typically used? (d) Should lexicographers invent their own examples or should they use authentic examples extracted from large bodies of textual data? (e) How do we make sure that the dictionaries really meet users' needs? (f) What kinds of navigation aid should be provided in learners' dictionaries? (g) Should a word be defined in a full sentence or in a telegraphic fashion? (h) What are collocations and how can they be identified in corpora and presented in a dictionary afterwards? (i) How should definitions be structured and written in a user-friendly way?