Dictionary Other variations

A miniature standard English dictionary combined with a thesaurus
Since words and their meanings develop over time, dictionary entries are organized to reflect these changes. Dictionaries may either list meanings in the historical order in which they appeared, or may list meanings in order of popularity and most common use.
Dictionaries also differ in the degree to which they are encyclopedic, providing considerable background information, illustrations, and the like, or linguistic, concentrating on etymology, nuances of meaning, and quotations demonstrating usage.
Any dictionary has been designed to fulfil one or more functions. The dictionary functions, or jobs, chosen by the maker(s) of the dictionary provide the basis for all lexicographic decisions, from the selection of entry words, over the choice of information types, to the choice of place for the information (e.g. in an article or in an appendix). There are two main types of functions. The communication-oriented functions comprise text reception (understanding), text production, text revision, and translation. The knowledge-oriented functions deal with situations where the dictionary is used for acquiring specific knowledge about a particular matter, and for acquiring general knowledge about something. The optimal dictionary is one that contains information directly relevant for the needs of the users relating to one or more of these functions. It is important that the information is presented in a way that keeps the lexicographic information costs at a minimum
Reference : http://en.wikipedia.org/wiki/Dictionary

Prescription description 2

The prescriptive/descriptive issue has been given so much consideration in modern times that most dictionaries of English apply the descriptive method to definitions, while additionally informing readers of attitudes which may influence their choices on words often considered vulgar, offensive, erroneous, or easily confused. Merriam-Webster is subtle, only adding italicized notations such as, sometimes offensive or nonstand (nonstandard.) American Heritage goes further, discussing issues separately in numerous "usage notes." Encarta provides similar notes, but is more prescriptive, offering warnings and admonitions against the use of certain words considered by many to be offensive or illiterate, such as, "an offensive term for..." or "a taboo term meaning..."
Because of the broad use of dictionaries, and their acceptance by many as language authorities, their treatment of the language does affect usage to some degree, even the most descriptive dictionaries providing conservative continuity. In the long run, however, usage primarily determines the meanings of words in English, and the language is being changed and created every day. As Jorge Luis Borges says in the prologue to "El otro, el mismo": "It is often forgotten that (dictionaries) are artificial repositories, put together well after the languages they define. The roots of language are irrational and of a magical nature."
Reference : http://en.wikipedia.org/wiki/Dictionary

Prescription description 1

Dictionary makers apply two basic philosophies to the defining of words: prescriptive or descriptive. Noah Webster, intent on forging a distinct identity for the American language, altered spellings and accentuated differences in meaning and pronunciation of some words. This is why American English now uses the spelling color while the rest of the English-speaking world prefers colour. (Similarly, British English subsequently underwent a few spelling changes that did not affect American English; see further at American and British English spelling differences.) Large 20th-century dictionaries such as the Oxford English Dictionary (OED) and Webster's Third are descriptive, and attempt to describe the actual use of words.

A dictionary open at the word "Internet", viewed through a lens
While descriptivists argue that prescriptivism is an unnatural attempt to dictate usage or curtail change, prescriptivists argue that to indiscriminately document "improper" or "inferior" usages sanctions those usages by default and causes language to "deteriorate". Although the debate can become very heated, only a small number of controversial words are usually affected. But the softening of usage notations, from the previous edition, for two words, ain't and regardless, out of over 450,000 in Webster's Third in 1961, was enough to provoke outrage among many with prescriptivist leanings, who branded the dictionary as "permissive."
Reference : http://en.wikipedia.org/wiki/Dictionary

Pronunciation

Dictionaries for languages for which the pronunciation of words is not apparent from their spelling, such as the English language, usually provide the pronunciation, often using the International Phonetic Alphabet. For example, the definition for the word dictionary might be followed by the (American English) phonemic spelling: . English dictionaries, however, often use other systems, such as the English Phonemic Representation system, in which the pronunciation of dictionary is given as [dĭk'shə-něr'ē]. Yet others use an ad hoc notation; for example, dictionary may become [DIK-shuh-ner-ee].
The online Turkish–English (and English–Turkish) dictionary Seslisozluk enables registered users to listen to the pronunciation of the words.
Reference : http://en.wikipedia.org/wiki/Dictionary

Dictionary Glossaries

Another variant is the glossary, an alphabetical list of defined terms in a specialised field, such as medicine or science. The simplest dictionary, a defining dictionary, provides a core glossary of the simplest meanings of the simplest concepts. From these, other concepts can be explained and defined, in particular for those who are first learning a language. In English, the commercial defining dictionaries typically include only one or two meanings of under 2000 words. With these, the rest of English, and even the 4000 most common English idioms and metaphors, can be defined.
Reference : http://en.wikipedia.org/wiki/Dictionary

Data dictionaries

Data sets and databases collected and utilized for statistical analyses are typically accompanied by, or able to be used to generate, a list of all variable names used within the data set, as well as matters such as their meaning, values, level of measurement, length, decimal allowances, and type (numeric, string, etc.)
Reference : http://en.wikipedia.org/wiki/Dictionary

Specialized dictionaries

According to the Manual of Specialised Lexicography a specialized dictionary (also referred to as a technical dictionary) is a lexicon that focuses upon a specific subject field. Following the description in The Bilingual LSP Dictionary lexicographers categorize specialized dictionaries into three types. A multi-field dictionary broadly covers several semantic fields (e.g., a picture dictionary), a single-field dictionary narrowly covers one particular subject field (e.g., law), and a sub-field dictionary covers a singular field (e.g., constitutional law). For example, the 23-language Inter-Active Terminology for Europe is a multi-field dictionary, the American National Biography is a single-field, and the African American National Biography Project is a sub-field dictionary. In terms of the above coverage distinction between "minimizing dictionaries" and "maximizing dictionaries", multi-field dictionaries tend to minimize coverage across lexical fields (for instance, Oxford Dictionary of World Religions) whereas single-field and sub-field dictionaries tend to maximize coverage within a limited subject field (The Oxford Dictionary of English Etymology). See also LSP dictionary.
Reference : http://en.wikipedia.org/wiki/Dictionary