Reference

In general, a reference is a relation between objects in which one object designates, or acts as a means by which to connect to or link to, another object. Such relations may occur in a variety of domains, including linguistics, logic, computer science, art, and scholarship. Thus, the objects to which the term reference applies may be of varying character ranging from concrete examples, such as a reference work in a library, as well as abstract objects, such as pointers in computer programming languages or symbols in language or mathematics. The nature of reference in its role in language and thought has been a prominent topic of discussion in philosophy since at least the 19th century and the logic work of J.S. Mill.

An object which is named by a reference, or to which the reference points, is called a referent.

The term reference is used with different specialized meanings in a variety of fields, as follows:

Semantics
In semantics, reference is generally construed as the relation between nouns or pronouns and objects that are named by them. Hence the word John refers to John. The word it refers to some previously specified object. The object referred to is called the referent of the word. Sometimes the word-object relation is called denotation; the word denotes the object. The converse relation, the relation from object to word, is called exemplification; the object exemplifies what the word denotes. In syntactic analysis, if a word refers to a previous word, the previous word is called the antecedent.

Reference and meaning
Frege argued that reference cannot be treated as identical with meaning: "Hesperus" (an ancient Greek name for the evening star) and "Phosphorus" (an ancient Greek name for the morning star) both refer to Venus, but the astronomical fact that '"Hesperus" is "Phosphorus"' can still be informative, even if the 'meanings' of both "Hesperus" and "Phosphorus" are already known. This problem led Frege to distinguish between the sense and reference of a word.

Absent referent
Words can often be meaningful without having a referent. Fictional and mythological names such as "Bo-Peep" and "Hercules" illustrate this possibility.

For those who argue that one cannot directly experience the divine (e.g. God), the sign "God" can serve as an example of a reference with an absent referent. Additionally, certain sects of Judaism and other religions consider it sinful to write, discard, or deface the name of the divine. To avoid this problem, the signifier G-d is sometimes used, though this could be seen as a sign which refers to another sign with an absent referent.

In mathematics, the absent referent can be seen with the symbol for zero, "0" or the empty set, "{ }".

Linguistic sign
The semantic sign can be considered a subset of a more general concept, the linguistic sign, first elucidated by Ferdinand de Saussure‎. A sign contains two parts, the signified (a thought which represents an object), and the signifier (the sound or written word). Both have a referent (the actual physical object). The sign is a building block for texts that supplies sound and meaning. The smallest building block is called a morpheme and may be lexical (carry lexical/encyclopedic meaning, e.g. refer to real-life entities) - or grammatical, i.e. combine with lexical ones, denoting another kind of reference - to actors (agreement), to time (tempus) etc., depending on the part of speech and indeed on the language.

Petrica Pomarleanu, Søren Kelstrup

Art
In Art, a reference is an item from which a work is based. This may include an existing artwork, a reproduced (i.e. photo) or directly observed (i.e. person) object, or the artist's memory.

Academic writing
In academic literature, a reference is a previously published written work within academic publishing which has been used as a source for theory or claims referred to which are used in the text. References contain complete bibliographic information so the interested reader can find them in a library. References can be added either at the end of the publication, or as footnotes.

Computer science
In computer science, references are datatypes which refer to an object elsewhere in memory, and are used to construct a wide variety of data structures such as linked lists. Most programming languages support some form of reference.

The C++ programming language has a specific type of reference also referred to as a reference; see reference (C++).

Geometry
A reference point is a location used to describe another one, by giving the relative position. Similarly we have the concept of frame of reference (both in physics and figuratively), benchmark (in surveying and figuratively), etc.

Libraries
In a library, the word reference may refer to a dictionary, encyclopedia, or other reference work that contains many brief articles that cover a broad scope of knowledge in one book, or a set of books. However, the word reference is also used to mean a book that cannot be taken from the room, or from the building. Many of the books in the reference department of a library are reference works, but some are books that are simply too large or valuable to loan out. Conversely, selected reference works may be shelved with other circulating books, and may be loaned out.

References to any type of printed matter come in electronic or at least machine-readable form nowadays. For books there exists the ISBN, for journal articles, the digital object identifier (DOI) is gaining relevance. Printed information on the Internet is usually referred to by some kind of uniform resource identifier (URI).

Scholarship
In scholarship, a reference may be a citation of a text that has been used in the creation of a piece of work such as an essay, report, or oration. Its primary purpose is to allow people who read such work to examine the author's sources, either for validity, or simply to learn more about the subject. Such items are often listed at the end of an article or book in a section marked Bibliography or in a section marked References. A Bibliography section will often contain work not cited by the author, but used as background reading or listed as potentially useful to the reader. A section labelled References should contain all and only work cited in the main text.

Copying of material by another author without proper citation or without required permissions amounts to 'plagiarism'.

Personal references
In the labour market, a reference is a letter to a prospective employer regarding a job applicant's characteristics. Usually the person providing the reference - the referee - is a previous boss, or someone of some distinction in the government, the clergy, or education, who can personally vouch for the applicant's employability; see also credit reference.

Canadian law
A Reference question, or "Reference" is a procedure through which the government of Canada can submit legal questions to the Supreme Court of Canada and provincial governments to the provincial courts of appeal.