The general meaning of the word 'dictionary' is that it is a reference book, giving information on particular subjects or on a particular class of words, names, or facts, usually arranged alphabetically, for example: a biographical dictionary. The dictionary catalogue derives its name from this general meaning of the word 'dictionary'. A dictionary catalogue gives information about documents available in a library with reference to their authors, titles, subjects, etc. All the entries getting arranged in a single alphabetical order. It resembles arrangement of entries as in a natural language dictionary in which all words, irrespective of their origin, parts of speech (nouns, verbs, adjectives, adverbs, etc.), usage, etc. are arranged in one single alphabetical order. A more formal definition of a dictionary catalogue is that it is 'a catalogue usually on cards, in which all entries - author, title, subjects, series, etc.,- and their relatives are arranged together in one general alphabet" (Anglo-American Cataloguing Rules IIAs mentioned above, a dictionary catalogue consists of four different groups of entries, each containing different types of bibliographical elements. The first group comprises authors and collaborators (editors, translators, commentators, etc.); the second group is composed of title entries.
The third group is made up of subject entries. The fourth group consists of cross-references of different kinds. But all these groups fall in one single alphabetical order. All theseentries are called word entries. Some libraries prefer to display the dictionary catalogue in two separate parts: the first part containing author and title entries with cross references, if any, and the second part is reserved exclusively for subject entries with cross references. This is called 'divided catalogue'. This type of separation poses some problems for users, as they have to refer to both these parts located at different places, to find out the information for a document of their interest. Although the dictionary catalogue is quite popular and widely used in libraries, it has its meritsand demerits.