Dictionary (late Lat. dictionarium), a book containing the words of a language alphabetically arranged, with their definitions and significations set forth more or less fully. In this respect it differs from a mere list or index, that it contains explanations about each word included within its scope, except where it is more convenient, by a cross-reference, to refer the reader for a part or the whole of the account of one word to what is said under some other word. There are several other terms that are used synonymously, or nearly so, with dictionary. The Greek word Lexicon is in common use for a dictionary of languages. It is not entirely so limited, however, in practice, as may be seen in such works as the Lexicon Juridicum of Calvinus or Kahl, which is just a dictionary of Roman and feudal law of the same kind as Sir Edward Tomlin's Law Dictionary is of English law. The word Encyclopædia has generally a wider meaning; but in actual use we find books of reference of exactly the same kind styled indifferently dictionaries and encyclopædias. The terms Glossary and Vocabulary are nearly synonymous with a dictionary of a language; and Thesaurus, Catalogue, Directory, Gazetteer, and Index are sometimes used as titles where dictionary might be not inapplicable.
Dictionaries may be divided into two classes—(1) those whose object is to explain words and phrases; and (2) those that aim at giving information about things.
(1) Dictionaries of language are, again, divided into various sub-classes or species. The most common kind—what, indeed, is understood by the term dictionary (and the equivalent Greek term Lexicon) when used by itself—is an alphabetical list of the words composing any language either explained in the same language, or interpreted by the corresponding words of one or more other languages. To indicate that all the words of the language are included, the name Thesaurus ('Treasury') is sometimes used, as in the great Hebrew dictionary of Gesenius. The words used by particular authors or classes of authors are often explained in special dictionaries or lexicons, such as those to Livy, Cicero, Tacitus, Homer, Sophocles, Shakespeare, and the like. A Glossary is a dictionary of unusual terms, as archaic, provincial, or technical terms. An etymological dictionary is one in which the derivation of words is the sole or a prominent object.
(2) Dictionaries of things (Ger. Realwörterbücher), or of information, are also of various kinds. When the whole field of human knowledge is embraced, we have an alphabetical Encyclopædia or Conversations-Lexicon. The name Encyclopædia or Cyclopædia is sometimes given to dictionaries of special departments of knowledge, as Anatomy and Physiology; but in all such cases dictionary seems the correcter term, as in the well-known dictionaries edited by Sir William Smith, which cover the whole ground of Bible terms, Greek and Roman biography and mythology and antiquities, Christian antiquities, and Christian biography.
There is no kind of information, within wide or narrow bounds, that may not be thrown into the dictionary form. Dictionaries of apt quotations from the classics, the Scriptures, or the fathers were not unknown in the 17th century. There are dictionaries of biography, of geography, of nautical terms, of dates, of architecture, of cookery, of political economy, of heraldry, of fortification—in fact, of every object of human knowledge and practice.
Dictionaries of language, in our sense of the word, are of modern origin. The Greeks and Romans had no idea of a book embracing all the words of their own or any foreign tongue. Glossaries, however, of unusual words and phrases were early current. The earliest work of the kind extant (though much interpolated) is the Homeric Lexicon (Gr. Lexis Homerikai) of Apollonius, an Alexandrine grammarian of the time of Augustus. More extensive compilations, such as the Lexicon of Suidas (q.v.), and the Etymologicum Magnum (q.v.), were made in the middle ages. A real dictionary became first possible after the invention of printing. A broad and sure basis for Greek lexicography was laid by Henry Stephens (q.v.) in his Thesaurus (1572), on which the school of Hemsterhuis built further, and which has been greatly extended by the labours of Schneider, Passow, Seiler, Jakobitz, Rost, and Pape. The well-known work of Liddell and Scott (7th ed. 1883) is based on the great German one of Passow. The Thesaurus (1531) of Robert Stephens inaugurated Latin lexicography, which has been extended by Joh. Matth. Gesner, Forcellini, Ducange (medieval Latin), Scheller, Freund, Georges, Mühlmann, and Vaniček, and is well represented in English by Riddell and White, Andrews, Smith, and the Americans Lewis and Short. The earliest standard dictionaries of modern tongues were the Italian Vocabolario della Crusca (1612); the Dictionary of the French Academy (1694); and that of the Academy at Madrid (1726–39). The great German Dictionary, begun in 1854 by the brothers Grimm, is still unfinished. Littre's French Dictionary (4 vols. and supplement) appeared in 1863–78. The materials collected by the Philological Society formed the main foundation for the great New English Dictionary, of which vols. i. and ii. were edited by Dr Murray (1888–93), in conjunction with Henry Bradley in vol. iii. and onwards. This splendid work follows a strictly historical method, and aims to give all the significations of every English word during the last seven hundred years, with a series of quotations illustrating its usage. English dictionary-making in its larger sense began with Dr Johnson (q.v.), the basis of whose work was an interleaved copy of Nathan Bailey's Dict. (1721–7).
The best complete English dictionaries at present in use are Richardson's, Worcester's, Webster's, Latham's edition of Johnson, Annandale's edition of Ogilvie's Imperial Dictionary, and especially the Century (6 vols. New York, 1889–91, edited by Whitney), and the Standard (2 vols. New York, 1893–95); for Scotch words, Jamieson (1808–25; ed. Donaldson, 1879–87); for etymology, those of Wedgwood, Edw. Müller (German), and Professor Skeat. The great Eng. Dialect Dictionary (ed. Wright) began in 1896, superseding Halliwell, T. Wright, &c. For older English words, the chief are Ælfric's Glossary (about 975), Way's edition (1843–65) of the Promptorium Parvulorum (about 1440), Bosworth's Anglo-Saxon Dictionary (ed. Toller), Stratmann's Middle-English Dictionary (ed. H. Bradley, 1891), Grein's Sprachschutz der Angelsächsischen Dichter, and Mätzner's Altenglische Sprachproben, &c.; as well also the Eng. words in Cotgrave's French-English Dict. (1611), Minshew's Guide into Tongues (1617), &c.—See BIOGRAPHY, ENCYCLOPÆDIA, DIALECT, ENGLISH, and articles on the various languages; also Vater's bibliography of dictionaries.