Mostly compiled as an aid to learning a foreign language, they are available in various sizes ranging from pocket size to multi-volume sets. British publishing firms Collins, Cambridge University Press, Cassell and Oxford University Press have provided a large number of bilingual dictionaries. Harrap of US are also a leading publisher of bilingual dictionaries from English to other European languages.
A typical English language bilingual dictionary offers a foreign word and its equivalent word in English in the first part. The process is reversed in the second part by giving the English word first followed by the equivalent foreign word. They are available in various sizes and volumes. They are well-illustrated by the members of the Harrap's family of French and English Dictionaries published simultaneously by Harrap at London and Scribner at New York.