What is "extension"

Extension \Ex*ten"sion\, n. [L. extensio: cf. F. extension. See Extend, v. t.]

1. The act of extending or the state of being extended; a stretching out; enlargement in breadth or continuation of length; increase; augmentation; expansion.

2. (Physics) That property of a body by which it occupies a portion of space.

3. (Logic & Metaph.)

   1. Capacity of a concept or general term to include a greater or smaller number of objects; -- correlative of intension.

   2. the class or set of objects to which a term refers; -- contrasted with intension, the logical specification which defines members of a class, being the set of attributes which are necessary and sufficient to recognize an object as a member of the class.

      The law is that the intension of our knowledge is in the inverse ratio of its extension.
      --Sir W. Hamilton.

      The extension of [the term] plant is greater than that of geranium, because it includes more objects.
      --Abp. Thomson.

4. (Surg.) The operation of stretching a broken bone so as to bring the fragments into the same straight line.

5. (Physiol.) The straightening of a limb, in distinction from flexion.

6. (Com.) A written engagement on the part of a creditor, allowing a debtor further time to pay a debt.

   Counter extension. (Surg.) See under Counter.

   Extension table, a table so constructed as to be readily extended or contracted in length.

c.1400, "swelling, bulging," from Latin extensionem/extentionem (nominative extensio/extentio) "a stretching out, extension," noun of action from past participle stem of extendere (see extend). In a concrete sense, "extended portion of something" (a railroad, etc.), from 1852. Telephone sense is from 1906.\n

n. 1 The act of extending or the state of being extended; a stretching out; enlargement in breadth or continuation of length; increase; augmentation; expansion. 2 That property of a body by which it occupies a portion of space (or time, e.g. "spatiotemporal extension") 3 (context semantics English) Capacity of a concept or general term to include a greater or smaller number of objects; — correlative of intension.

1. n. a mutually agreed delay in the date set for the completion of a job or payment of a debt; "they applied for an extension of the loan"

2. act of expanding in scope; making more widely available; "extension of the program to all in need"

3. the spreading of something (a belief or practice) into new regions [syn: propagation]

4. an educational opportunity provided by colleges and universities to people who not enrolled as regular students [syn: extension service, university extension]

5. act of stretching or straightening out a flexed limb [ant: flexion]

6. a string of characters beginning with a period and followed by one to three letters; the optional second part of a PC computer filename; "most applications provide extensions for the files they create"; "most BASIC files use the filename extension .BAS" [syn: filename extension, file name extension]

7. the most direct or specific meaning of a word or expression; the class of objects that an expression refers to; "the extension of `satellite of Mars' is the set containing only Demos and Phobos" [syn: reference, denotation]

8. the ability to raise the working leg high in the air; "the dancer was praised for her uncanny extension"; "good extension comes from a combination of training and native ability"

9. amount or degree or range to which something extends; "the wire has an extension of 50 feet" [syn: lengthiness, prolongation]

10. an additional telephone set that is connected to the same telephone line [syn: telephone extension, extension phone]

11. an addition to the length of something [syn: elongation]

12. an addition that extends a main building [syn: annex, annexe, wing]

Extension, extend or extended may refer to:

In music, an extension is a set of musical notes that lie outside the standard range or tessitura.

Extension is the third album by American saxophonist George Braith recorded in 1964 and released on the Blue Note label.

Extension is the third album by composer/arranger/keyboardist Clare Fischer, and his first for big band, recorded and released in 1963 on the Pacific Jazz label, reissued on CD (together with the 1967 LP, Songs for Rainy Day Lovers) in 2002 as America the Beautiful, and, under its original name, in 2012.

In metaphysics, extension is, roughly speaking, the property of "taking up space". René Descartes defines extension as the property of existing in more than one dimension. For Descartes, the primary characteristic of matter is extension, just as the primary characteristic of mind is consciousness. This can be contrasted with , where the Planck length, an almost unimaginably tiny quantity, represents reaching that distance scale where, it has been theorized, all measurement seemingly breaks down to that which can be subsumed at this scale, as distance only, or extension.

John Locke, in An Essay Concerning Human Understanding, defined extension as "only the Space that lies between the Extremities of those solid coherent Parts" of a body. It is the space possessed by a body. Locke refers to the extension in conjunction with solidity and impenetrability, the other primary characteristics of matter.

Extension also plays an important part in the philosophy of Baruch Spinoza, who says that substance (that which has extension) can be limited only by substance of the same sort, i.e. matter cannot be limited by ideas and vice versa. From this principle, he determines that substance is infinite. This infinite substance is what Spinoza calls God, or better yet nature, and it possesses both unlimited extension and unlimited consciousness.

The property of extension has not played a significant role in philosophy roughly since the time of Immanuel Kant. Kant maintained a distinction between the mind and the body, differentiating space as the realm of the body and time the realm of the mind. He makes only cursory mention of "extension," however, and no philosophers have dealt extensively with the topic since Kant's writing.

In any of several studies that treat the use of signs — for example, in linguistics, logic, mathematics, semantics, and semiotics — the extension of a concept, idea, or sign consists of the things to which it applies, in contrast with its comprehension or intension, which consists very roughly of the ideas, properties, or corresponding signs that are implied or suggested by the concept in question.

In philosophical semantics or the philosophy of language, the 'extension' of a concept or expression is the set of things it extends to, or applies to, if it is the sort of concept or expression that a single object by itself can satisfy. Concepts and expressions of this sort are monadic or "one-place" concepts and expressions.

So the extension of the word "dog" is the set of all (past, present and future) dogs in the world: the set includes Fido, Rover, Lassie, Rex, and so on. The extension of the phrase "Wikipedia reader" includes each person who has ever read Wikipedia, including you.

The extension of a whole statement, as opposed to a word or phrase, is defined (since Frege 1892) as its truth value. So the extension of "Lassie is famous" is the logical value 'true', since Lassie is famous.

Some concepts and expressions are such that they don't apply to objects individually, but rather serve to relate objects to objects. For example, the words "before" and "after" do not apply to objects individually — it makes no sense to say "Jim is before" or "Jim is after" — but to one thing in relation to another, as in "The wedding is before the reception" and "The reception is after the wedding". Such "relational" or "polyadic" ("many-place") concepts and expressions have, for their extension, the set of all sequences of objects that satisfy the concept or expression in question. So the extension of "before" is the set of all (ordered) pairs of objects such that the first one is before the second one.

On the Apple Macintosh operating system prior to OS X, extensions were small pieces of code that extended the system's functionality. They were run initially at start-up time, and operated by a variety of mechanisms, including trap patching and other code modifying techniques. Initially an Apple developer hack, extensions became the standard way to provide a modular operating system. Large amounts of important system services such as the TCP/IP network stacks (MacTCP and Open Transport) and USB and FireWire support were optional components implemented as extensions. The phrase "system extension" later came to encompass faceless background applications as well.

Extensions generally filled the same role as DOS's terminate and stay resident programs, or Unix's daemons, although by patching the underlying OS code, they had the capability to modify existing OS behaviour the other two did not.

The extension of a predicatea truth-valued functionis the set of tuples of values that, used as arguments, satisfy the predicate. Such a set of tuples is a relation.

For example the statement "d2 is the weekday following d1" can be seen as a truth function associating to each tuple (d2, d1) the value true or false. The extension of this truth function is, by convention, the set of all such tuples associated with the value true, i.e.

{(Monday, Sunday),
(Tuesday, Monday),
(Wednesday, Tuesday),
(Thursday, Wednesday),
(Friday, Thursday),
(Saturday, Friday),
(Sunday, Saturday)}

By examining this extension we can conclude that "Tuesday is the weekday following Saturday" (for example) is false.

Using set-builder notation, the extension of the n-ary predicate Φ can be written as

{(x, ..., x) ∣ Φ(x, ..., x)} .

In residential telephony, an extension telephone is an additional telephone wired to the same telephone line as another. In middle 20th century telephone jargon, the first telephone on a line was a "Main Station" and subsequent ones "Extensions". Such extension phones allow making or receiving calls in different rooms, for example in a home, but any incoming call would ring all extensions and any one extension being in use would cause the line to be busy for all users. Some telephones intended for use as extensions have built in intercom features; a key telephone system for a small business may offer two to five lines, lamps indicating lines already in use, the ability to place calls on ' hold' and an intercom on each of the multiple extensions.

In business telephony, a telephone extension may refer to a phone on an internal telephone line attached to a private branch exchange (PBX) or Centrex system. The PBX operates much as a community switchboard does for a geographic telephone numbering plan and allows multiple lines inside the office to connect without each phone requiring a separate outside line. In these systems, one usually has to dial a number (typically 9 in North America, 0 in Europe) to tell the PBX to connect with an outside landline (also called DDCO, or Direct Dial Central Office) to dial an external number. Within the PBX, the user merely dials the extension number to reach any other user directly. For inbound calls, a switchboard operator or automated attendant may request the number of the desired extension or the call may be completed with direct inbound dialing if outside numbers are assigned to individual extensions.

An off-premises extension, where a worker at a remote location employs a telephone configured to appear as if it were an extension located at the main business site, may be created in analog telephony by using a leased line to connect the extension to the main enterprise system. Voice over IP makes the creation of off-premises extensions inexpensive and trivial as broadband Internet and virtual private networking can extend local network access anywhere in the world. In either system, an off-premises extension is reachable from within the same enterprise simply by calling its extension number directly; for inbound and outgoing calls, it functions as if it were located at the main place of business.