In a computer language, a reserved word (also known as a reserved identifier) is a word that cannot be used as an identifier, such as the name of a variable, function, or label – it is "reserved from use".
This is a syntactic definition, and a reserved word may have no meaning.
A closely related and often conflated notion is a keyword which is a word with special meaning in a particular context.
This is a semantic definition.
By contrast, names in a standard library but not built into the language are not considered reserved words or keywords.
The terms "reserved word" and "keyword" are often used interchangeably – one may say that a reserved word is "reserved for use as a keyword" – and formal use varies from language to language; for this article we distinguish as above.
In general reserved words and keywords need not coincide, but in most modern languages keywords are a subset of reserved words, as this makes parsing easier, since keywords cannot be confused with identifiers.
In some languages, like C or Python, reserved words and keywords coincide, while in other languages, like Java, all keywords are reserved words, but some reserved words are not keywords – these are "reserved for future use".
In yet other languages, such as ALGOL and PL/I there are keywords but no reserved words, with keywords being distinguished from identifiers by other means.
In corpus linguistics a key word is a word which occurs in a text more often than we would expect to occur by chance alone.
Key words are calculated by carrying out a statistical test (e.g., loglinear or chi-squared) which compares the word frequencies in a text against their expected frequencies derived in a much larger corpus, which acts as a reference for general language use.
Advance Keyword Explanation
An index term, subject term, subject heading, or descriptor, in information retrieval, is a term that captures the essence of the topic of a document.Index terms make up a controlled vocabulary for use in bibliographic records.
They are an integral part of bibliographic control, which is the function by which libraries collect, organize and disseminate documents.
They are used as keywords to retrieve documents in an information system, for instance, a catalog or a search engine.
A popular form of keywords on the web are tags which are directly visible and can be assigned by non-experts also.
Index terms can consist of a word, phrase, or alphanumerical term.
They are created by analyzing the document either manually with subject indexing or automatically with automatic indexing or more sophisticated methods of keyword extraction.
Index terms can either come from a controlled vocabulary or be freely assigned.
Keywords are stored in a search index.
Common words like articles (a, an, the) and conjunctions (and, or, but) are not treated as keywords because it is inefficient to do so.
Almost every English-language site on the Internet has the article "the", and so it makes no sense to search for it.
The most popular search engine, Google removed stop words such as "the" and "a" from its indexes for several years, but then re-introduced them, making certain types of precise search possible again.
The term "descriptor" was coined by Calvin Mooers in 1948.
It is in particular used about a preferred term from a thesaurus.
The Simple Knowledge Organisation System language (SKOS) provides a way to express index terms with Resource Description Framework for use in the context of Semantic Web.[1]
In Digital Search Engines
Most digital search engines are designed to search for words anywhere in a document- the title, the body, and so on.This being the case, a keyword can be any term that exists within the document.
However, priority is given to words that occur in the title, words that recur numerous times, and words that are explicitly assigned as keywords within the coding.[2]
Index terms can be further refined using "Boolean operators" such as "and, or, not." "And" is normally unnecessary as most search engines infer it.
"Or" will search for results with one search term or another, or both. "Not" eliminates a word or phrase from the search, getting rid of any results that include it.
Multiple words can also be enclosed in quotation marks to turn the individual index terms into a specific index phrase.
These modifiers and methods all help to refine search terms, to better maximize the accuracy of search results.[3]
Author keywords
Many journals and databases provides access (also) to index terms made by authors to the articles being published or represented.The relative quality of indexer-provided index terms and author provided index terms is of interest to research in information retrieval.
The quality of both kinds of indexing terms depends, of course, on the qualifications of provider.
In general authors have difficulties providing indexing terms that characterizes his document relative to the other documents in the database.
Author keywords are an integral part of literature.[1]
Google Adwords Planner
Google Adwords' Keyword Planner tool is a product from Google Adwords which provides data around the search queries that happen in Google and other resources for planning a Google Adwords specific advertising campaign.[1]
Google Keyword Planner[2] is a tool that helps to build new Search Network campaigns or expand existing campaigns.
It will help you to get keywords and ad group ideas, historical statistics, keywords trend, competitions, bidding etc.
This service is free offered buy Google; anyone can use it without spending single penny.
Market Places such as ClickBank, Ebay, Amazon, or the Top Three seach Engines themselves are great places to find Keywords.
Source: Wikipedia.org
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