Definition of extension in English:

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Pronunciation: /ˌikˈsten(t)SH(ə)n/


1A part that is added to something to enlarge or prolong it; a continuation: the railroad’s southern extension
More example sentences
  • As the director explains in the program, the musical additions are an extension of the opening line: ‘If music be the food of love, play on.’
  • We will use this system as an extension of our network to get to additional buildings and customers and to reach into cities where we don't have significant buildouts.
  • I noted the vapor trails that were draped along the leading edge extensions and wingtips as he passed overhead - telltale signs of a high-performance turn.
1.1A room or set of rooms added to an existing building.
Example sentences
  • The use of the main building and the extension has caused problems to adjacent residents for a number of years and is currently the subject of an ombudsman's complaint against the Council.
  • Its plans also include an extension to the main building and a new, separate stable block as well as an upgraded driveway and access to the main road.
  • The in-patient Assessment Unit occupies a modern, purpose-built, sympathetic extension to the main building.
1.2The action or process of becoming or making something larger: the extension of the president’s powers
More example sentences
  • In addition, the extension of the Dart line to Greystones offers another choice for commuters to the city.
  • The basic family unit is universal, as is its extension to create an additional sense of comfort and protection within communities, tribes or nations.
  • The extension to the original building was seamlessly carried out, so it is almost impossible to identify the earlier work.
expansion, increase, enlargement, widening, broadening, deepening;
augmentation, enhancement, development, growth, continuation
1.3An application of an existing system or activity to a new area: direct marketing is an extension of telephone selling
More example sentences
  • Also to come under the umbrella of the project is the town of Kiltimagh which will be provided with additional broadband capacity as an extension of the Ballina scheme.
  • The word ‘refer’, in our submission, is the trigger in each of those parts to the extension or additional application of that part.
  • In the early days of the net, the ITU saw the network as an extension of the international telephone network that it oversees.
1.4An increase in the length of time given to someone to hold office, complete a project, or fulfill an obligation.
Example sentences
  • Earning the respect of his players after a rocky start three seasons ago, Hartley was given a well-deserved raise and two-year extension.
  • During the meeting, the board gave the president a two-year contract extension and a raise.
  • As well, I note that the section is discretionary, meaning that even if the criteria are met, the application for extension may be denied for other reasons.
prolongation, lengthening, increase
postponement, more/extra time, deferral, delay
1.5 Computing An optional suffix to a file name, typically consisting of a period followed by several characters, indicating the file’s content or function.
Example sentences
  • Once I have a domain name, I can add aliases and extensions to define additional systems and services.
  • Most times the extension is the substring which follows the last occurrence, if any, of the dot character.
  • Be aware though that there is no standardization to filename extension usage, and many different people have used extensions to apply to many different things.
2 (also extension cord) A length of electric cord that permits the use of an appliance at some distance from a fixed socket.
Example sentences
  • Floodwaters have caused much damage and several extensions and additional pieces of equipment are urgently needed.
  • This little extension gives you the ability to plug it in regardless of the USB landscape you are dealing with.
  • These may be considered either as powercords (if IEC outlets are in use) or as extensions (if used to extend a powercord).
2.1An extra telephone on the same line as the main one.
Example sentences
  • Mrs. Jacobs, who had been listening in on an extension, (with Vera's knowledge), offered to drive her to the hospital.
  • With Maddox listening in on the extension, Astor asked Signor Altaverdi if he needed any further copies of the surveillance photographs and told him that he hoped to be back in Italy after the weekend.
  • I wish I didn't have a phone extension in my bedroom, I think lazily.
2.2A subsidiary telephone in a set of offices or similar building, on a line leading from the main switchboard but having its own additional number.
Example sentences
  • Handsets will be allotted extension numbers in addition to their handphone numbers.
  • I was totally overwhelmed and attempted to cope the best I could, as did the general hospital switchboard, with its extensions all manually connected through an operator in those days.
  • I listened in on an extension when Frank phoned Jack at Bute House to be told his fate.
3 [usually as modifier] Instruction by a university or college for students who do not attend full time: extension courses
More example sentences
  • Every university should have an extension department to promote students' participation in community-based activities.
  • As the school's night college, the extension school attracts extraordinary students.
  • The Food Innovation Center, a branch of Oregon State University's agricultural extension service, is based in Portland.
4 (extensions) Lengths of real or artificial hair woven into a person’s own hair to create a long hairstyle.
Example sentences
  • You can have an intricate patterns of different colors or beads added to the extension without additional damage to your hair.
  • As the top United Kingdom retailer of clip in hair extension and human hair products, we offer you only the best the industry has to offer.
  • Our real human hair clip on extensions are very easy to use and not noticeable, and it won't damage your own hair.
5The action of moving a limb from a bent to a straight position: seizures with sudden rigid extension of the limbs
More example sentences
  • Muscle bulk, tone and strength were normal, but she displayed decreased range of motion in internal and external rotation, flexion and extension of both shoulders.
  • The spams are a type of seizure associated with sudden flexion or extension movements.
  • Sprains and strains may occur with a variety of athletic activities and are more likely to occur with sudden movements involving spinal extension and rotation.
5.1The muscle action controlling this: triceps extension
More example sentences
  • Eukaryotic cells move by a complex mechanism of extension and retraction controlled by the cytoskeleton dynamical assembly.
  • Hip - joint extension and the muscles involved are essential in running, jumping, diving, gymnastics and the martial arts.
  • Another variation of this exercise is the standing overhead triceps extension.
5.2 Ballet The ability of a dancer to raise one leg above the waist, or an instance of this: she has amazing extension he could perform 180-degree extensions
More example sentences
  • So instead of 180 degrees of extension per double push, he'll get 130 or 140, which is more than 90.
  • I have read your advice on extensions and there is one I have a problem with.
  • Remember that extension is strength and placement as well as flexibility.
5.3 Medicine The application of traction to a fractured or dislocated limb or to an injured or diseased spinal column to restore it to its normal position.
Example sentences
  • An evaluation for effusion should be conducted with the patient supine and the injured knee in extension.
  • Posterior elbow pain in the setting of repetitive elbow extension suggests the diagnosis of triceps tendinosis.
  • Adolescents with spondylolysis or spondylolisthesis experience an exacerbation of lumbosacral pain with spinal extension.
5.4The lengthening of a horse’s stride within a particular gait.
Example sentences
  • The road horse trot is a fast-stepping trot - characterized by length and rapidity and executed with extreme degree of extension or length of stride.
  • To get that extension where the horse really sits back and goes slowly while making huge strides, the horse is ridden from behind uphill to the extension.
6 Logic The range of a term or concept as measured by the objects that it denotes or contains, as opposed to its internal content. Often contrasted with intension.
Example sentences
  • To make sure that the extension of the definiens matches that of the definiendum, Beardsley thinks, the second disjunct of the definition is needed.
  • So the extension of the term ‘marsupial’ is the set of all marsupials: kangaroos, wallabies, wombats, and so on.
  • Put in modern terms, Abelard holds a theory of direct reference, in which the extension of a term is not a function of its sense.
6.1 Physics & Philosophy The property of occupying space; spatial magnitude: nature, for Descartes, was pure extension in space
More example sentences
  • Space was the empty extension that allowed his bits of matter - his atoms - to move about.
  • Regardless, physical extension seems nothing more than a relational property as well: the quality of extension in space is not possible without relations amongst constituent parts.
  • This is obvious from our inability to conceive of a half or a third of a soul, or of the extension which a soul occupies.


by extension

Taking the same line of argument further: this raised serious questions about his credibility and, by extension, the credibility of the company
More example sentences
  • But from past experience, I doubt that any serious combat, and by extension deaths, will occur.
  • That would be the boards of directors, and, by extension, the stockholders.
  • The drawing itself is often used as an implied symbol of the essential symmetry of the human body, and by extension, to the universe as a whole.



Pronunciation: /-SHənl/
Example sentences
  • Bent specimens show folds on the compressional but not the extensional side, indicating that walls were originally flexible.
  • On the island of Ikaria in the eastern Aegean Sea, a low-angle extensional ductile shear zone and two associated brittle detachment faults are well exposed.
  • It is proposed that evaporite dissolution led to the collapse of the weakly lithified overburden, and this deformed with a series of concentric extensional faults.


Late Middle English: from late Latin extensio(n-), from extendere 'stretch out' (see extend).

Words that rhyme with extension

abstention, apprehension, ascension, attention, circumvention, comprehension, condescension, contention, contravention, convention, declension, detention, dimension, dissension, gentian, hypertension, hypotension, intention, intervention, invention, mention, misapprehension, obtention, pension, prehension, prevention, recension, retention, subvention, supervention, suspension, tension

For editors and proofreaders

Syllabification: ex·ten·sion

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