Definition of extension in US English:



  • 1A part that is added to something to enlarge or prolong it; a continuation.

    ‘the railroad's southern extension’
    • ‘When he again looked outside during the descent, I had disappeared under his leading-edge extension.’
    • ‘Station improvements are being considered for Shenfield while Gidea Park, Harold Wood and Brentwood are in line for platform extensions and station revamps.’
    • ‘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.’
    • ‘These courtyards are designed as extensions of the surrounding buildings, serving as outdoor teaching and study rooms.’
    • ‘The MSO must repeat its surveys of housing density use to identify places where the level of growth qualifies for line extensions without the customer contributing to the cost.’
    • ‘He said he's looking forward to the extension of the 2000 line, which will enable it to handle high-definition television as well.’
    • ‘It is not officially a branch, but rather an extension of the main line first named the Oshawa Subdivision and re-named the Belleville Subdivision.’
    • ‘The extension adds an additional round to the magazine, plus it makes the small Glock more comfortable to shoot.’
    • ‘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.’’
    • ‘When these were recommended for refusal, the plans were resubmitted to propose one additional jetty and an extension on the current one.’
    • ‘The obvious worry is that the site will come under the control of the prime minister's press spokesman and therefore become little more than an extension of the Party line.’
    • ‘This provides an additional extension of endogenous origin, accommodated by further deformation.’
    • ‘The East London line extensions have backing of almost all of London's elected representatives and possess a solid business case approved by the Strategic Rail Authority.’
    • ‘But for most people now, their mobile phone is an extension of their arm and they always have it with them.’
    • ‘As in all ophiacodontids, the iliac blade of the Ada Ophiacodon is a straight dorsoposterior extension with no anterior expansion.’
    • ‘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.’
    • ‘Gables, by the way, are actual extensions of the roof line and are not to be confused with dormer windows, which can spring up in the middle of a section of roof.’
    • ‘Greig said the proposed M74 extension around the south side of Glasgow would help to take traffic off the M8 but this was still some years away.’
    • ‘Part of the growth, clearly, comes from the heavy-hitting brands bringing out new line extensions, hoping to catch the lightning in a bottle.’
    addition, add-on, adjunct, addendum, augmentation, supplement, appendage, appendix
    View synonyms
    1. 1.1 A room or set of rooms added to an existing building.
      • ‘There will have to be consultation with English Heritage, but the council hopes there will be a glass extension to the building, as a new main entrance from Vernon Street.’
      • ‘He redecorated the building and added extensions.’
      • ‘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.’
      • ‘While combining the buildings, the extension also expresses historical division.’
      • ‘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.’
      • ‘The indoor markets in the building extension hereby approved shall be held solely on Saturdays and Sundays and on no other day of the week whatsoever…’
      • ‘With an abundance of space to all sides, the property has potential for the development of a sizeable extension or additional accommodation on its site subject to planning permission.’
      • ‘Peter is clearly in a dominant position as his bank is holding itself out as possessing some type of specialist skill, i.e. co-ordinating the planning and building of house extensions.’
      • ‘She plans to add an additional extension to the front of the house before the builders pack up and leave.’
      • ‘In Galway, contribution rates for residential units differ depending on location, and people building extensions to private houses don't pay a contribution fee.’
      • ‘The building was a meek, red brick building with several extensions to make up for the growth in attendance every year.’
      • ‘The free-standing, sky-blue core can be glimpsed as you move through the building and a canted link corridor connects the new extension with the main laboratory.’
      • ‘Their target was the Marine Security Detachment Headquarters, a small extension on the four story main Embassy building.’
      • ‘It is made up of three interconnecting Georgian buildings with a modern extension at the back and has 18 parking spaces.’
      • ‘The in-patient Assessment Unit occupies a modern, purpose-built, sympathetic extension to the main building.’
      • ‘The first move was to clear the hospital building of ad-hoc extensions, and retrieve the original Blacket structure.’
      • ‘She said the high rates had forced the association to offer its present property for sale as it did not have enough funds to use the land for the building extensions once planned.’
      • ‘His first task was to design and equip the new museum, part of a planned extension of the main university building.’
      addition, add-on, adjunct, addendum, augmentation, supplement, appendage, appendix
      View synonyms
    2. 1.2extensions Lengths of real or artificial hair woven into a person's own hair to create a long hairstyle.
      • ‘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.’
    3. 1.3 The action or process of becoming or making something larger.
      ‘the extension of the President's powers’
      • ‘In addition, the extension of the Dart line to Greystones offers another choice for commuters to the city.’
      • ‘It was characterised primarily by the fact of extension: it occupied space and was therefore amenable to measurement.’
      • ‘The basic family unit is universal, as is its extension to create an additional sense of comfort and protection within communities, tribes or nations.’
      • ‘In amphibians, there is convergent extension of the future neural plate during gastrulation.’
      • ‘To a degree this extension of powers was nominal rather than real, for much was a rationalization and codification of hitherto haphazard statute and common law, or a legitimation of what was already police practice.’
      • ‘The same group of people would miss out on an extension of the telephone allowance.’
      • ‘The extension to the original building was seamlessly carried out, so it is almost impossible to identify the earlier work.’
      • ‘The extension of the canting space at deepwater berths to provide for vessels up to 450 feet long is at present in hand.’
      • ‘The linking of environmental requirements to direct payments under EU support and subsidisation schemes was a natural extension of this line of thinking.’
      expansion, increase, enlargement
      View synonyms
    4. 1.4 An application of an existing system or activity to a new area.
      ‘direct marketing is an extension of telephone selling’
      • ‘Popular in projections and textbooks, line extensions should however come with a warning: handle with care; this can be hazardous to your bottom line.’
      • ‘New apparel, plush and extensions of the toy line are planned.’
      • ‘In the early days of the net, the ITU saw the network as an extension of the international telephone network that it oversees.’
      • ‘The EMEAP working group will proceed to study the extension of the ABF concept to include bonds denominated in regional currencies.’
      • ‘Demand for cosmetics and toiletries is increasing, as can be seen in the constant introduction of new products and the trend towards brand and line extensions, Euromonitor says.’
      • ‘Men 18-34 are more inclined to look beyond buying just a fragrance and aftershave; they're moving on to line extensions.’
      • ‘Similar commitments by all five of the nuclear powers were essential to gain support for the 1995 extension of the Nuclear Nonproliferation Treaty.’
      • ‘As such, offering managed telephony services is a natural extension of their business model.’
      • ‘Loopy line extensions are not new phenomena; they've just become increasingly dizzying with many often mystifying leaps.’
      • ‘Currently the preimplantation selection of embryos is restricted to cases of serious diseases, but the authors urged caution in the future extension of this application.’
      • ‘Saying it's all linguistics is a bit of a strange thing to say, since most of Derrida's work is an extension from work that was itself an extension of Structural Linguistics.’
      • ‘The principal one, a child of its times, was molecular associationism, a metaphoric extension of the atomism of nineteenth-century physics.’
      • ‘The word ‘refer’, in our submission, is the trigger in each of those parts to the extension or additional application of that part.’
      • ‘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.’
      • ‘They also avoided medical waste, which was controlled by the mob, a high profit extension to the Family owned hauling firms.’
      • ‘Four years later Dirac's positron was also found in a cosmic ray shower and in 1933 Dirac was awarded the Nobel Prize in Physics for his extension of atomic theory.’
      • ‘By June, nearly 35% of the prescriptions being written were for one of the line extensions, according to Ravera.’
      • ‘Consequently, processors have continued their R&D efforts in the kids' yogurt segment, rolling out numerous line extensions in recent months.’
      • ‘At a time when cereal marketing has devolved to price-cutting and me-too line extensions, that's an aggressive marketing push.’
      expansion, development, progress, advance, advancement, headway, improvement, furtherance, spread, buildout, escalation
      View synonyms
    5. 1.5 An increase in the length of time given to someone to hold office, complete a project, or fulfill an obligation.
      • ‘An alternative construction would be that the late fees were intended to be rental payments for an extension of the term and that the replacement fees were the purchase price of unreturned videos.’
      • ‘One is the former one of an application for extension of time for service of the summons - I do not apprehend it will be opposed.’
      • ‘The opposition Socialist Party argued against an extension, saying emergency measures were no longer needed because violence is abating.’
      • ‘This means that 318 individual applications for review and extension would be needed.’
      • ‘During the meeting, the board gave the president a two-year contract extension and a raise.’
      • ‘Because of this conclusion the application fails and the application for extension of time is rejected.’
      • ‘In terms of the long and chequered history of policing in the North, the extension of his term by the Policing Board is of little consequence.’
      • ‘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.’
      • ‘As I understand it, no one took issue with our lateness, and we did put on an application for extension of time in the second one, as I understand it.’
      • ‘It is not uncommon on applications for special leave to appeal to have to deal with applications for extension of time, and that can be dealt with then.’
      • ‘We would submit why should it be any different, as long as some evidence is put before the court to the effect that there is a proposed application for extension.’
      • ‘Earning the respect of his players after a rocky start three seasons ago, Hartley was given a well-deserved raise and two-year extension.’
      • ‘Accordingly the application for extension of time is refused.’
      • ‘There is an application for extension of time which I understand is not opposed.’
      • ‘Any distribution of any part of the estate made before the application for extension of time shall not be disturbed by reason of that application or any order made thereon.’
      • ‘Subject to the outcome of the application for extension of time, there will be a cross-appeal, yes, as I am instructed.’
      • ‘The CEO was able to get out of his lease and into cheaper space, negotiate interest-free extensions on his debt, and significantly reduce operating costs.’
      • ‘Some of the applications for extension were made before the Court of Appeal decided the matters; some were made after judgment was given.’
      • ‘Does that not suggest that we ought to be dealing with an application for extension of time?’
      • ‘I will remit this application, including any application for extension of time to the Federal Magistrates Court of Australia.’
      prolongation, lengthening, increase, protraction, continuation, perpetuation
      postponement, deferral, delay
      View synonyms
    6. 1.6Computing An optional suffix to a file name, typically consisting of a period followed by several characters, indicating the file's content or function.
      • ‘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.’
  • 2A length of electric cord that permits the use of an appliance at some distance from a fixed socket.

    • ‘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).’
    • ‘Instead of just having power outputs on one end of an extension cord, designer Wilson Song placed them all along the cord itself.’
  • 3An extra telephone on the same line as the main one.

    • ‘Prudie finds this issue akin to a spouse or family member listening in on an extension.’
    • ‘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.’
    • ‘John Y. Brown, owner of the Buffalo Braves, called Fitz, who had me pick up the extension and listen in.’
    • ‘By this time, Vera had picked up an extension, and was listening in on the conversation, in Charlie's presence.’
    • ‘This response mode ensured the privacy of adolescents' responses, in the event that parents or siblings were listening to the interview on a telephone extension.’
    • ‘Mrs. Jacobs, who had been listening in on an extension, (with Vera's knowledge), offered to drive her to the hospital.’
    • ‘I wish I didn't have a phone extension in my bedroom, I think lazily.’
    1. 3.1 A subsidiary telephone in a set of offices or similar building, on a line leading from the main switchboard but having its own additional number.
      • ‘Nigel took charge of the cigarette while Pru used the ground-floor extension of the internal telephone system.’
      • ‘For corporations that want extensions and services that are even more closely identified with PBXs uncovered in the corporate globe, this system isn't a very good option.’
      • ‘Lexmark has, however, restored the errant phone extension.’
      • ‘My door will be knocked down with people looking for line extensions,’ he said.’
      • ‘Which type of these phone systems you choose will depend on the amount of extensions you require and the features your telephone system needs to have installed.’
      • ‘His place of work is the Resource Library at St. Ann Street Police Station where all other officers have access and he is without a telephone extension.’
      • ‘Their reasoning is that with an ever-increasing demand to handle new products and line extensions, and given their high failure rate, they feel they need help in dealing with the cash flow and overhead involved.’
      • ‘McCarthy returned the favor by letting Anderson listen on the extension during supposedly confidential conversations with Republican leaders.’
      • ‘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.’
      • ‘Look at how many lines and extensions you have at the moment and decide how many your company may require in the future.’
      • ‘Handsets will be allotted extension numbers in addition to their handphone numbers.’
      • ‘Perhaps the Minister could call John Tamihere and tell him that my telephone extension is 6262, so he can communicate to this House just what he thinks of this bill.’
      • ‘All MSPs need do is pick up the phone, provide their telephone extension, and the cab is on its way.’
      • ‘I would be grateful if you could contact me on the above extension to let me know whether you are coming into the Office or whether you would prefer a home visit.’
  • 4The action of moving a limb from a bent to a straight position.

    ‘seizures with sudden rigid extension of the limbs’
    • ‘Muscle endurance testing can be performed with sustained upward gaze, neck extension while in the prone position, and arm abduction against resistance or gravity.’
    • ‘The extension of the leading arm as already discussed is one of the most significant skills to be mastered.’
    • ‘The patient was distressed on flexion, extension, and internal rotation of the right hip.’
    • ‘The knee examination is normal, but hip pain is elicited with passive internal rotation or extension of the affected hip.’
    • ‘Hood, a general practitioner, was interested in the movements of flexion and extension, combined with external pressure, used by bone setters for back injuries.’
    • ‘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.’
    • ‘Standing thoracic and lumbar extension and seated thoracic rotation may be useful therapeutic exercises for patients in the acute and subacute stages of healing.’
    • ‘These motions are more complex than simple flexion and extension.’
    • ‘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.’
    • ‘Normal hip range of motion includes abduction, adduction, circumduction, extension, and flexion.’
    • ‘The spams are a type of seizure associated with sudden flexion or extension movements.’
    • ‘The straight thrust is a simple, direct extension of the arm used with either a lunge or flèche to touch the opponent.’
    • ‘Range of motion, including flexion, extension, lateral rotation and lateral bending, should be assessed.’
    • ‘Finally, the provocative test for snapping the iliopsoas tendon is to bring the hip back and forth between flexion and external rotation and extension and internal rotation.’
    • ‘And he was tested at between 10 and 14 degrees of elbow extension during the bowling of the doosra.’
    • ‘Pain is often localised, is worse with extension and rotation, and may be troublesome at night.’
    • ‘No physical evidence of any other movement than knee extension was observed during the stimulations.’
    • ‘This can be associated with the distal extension of the limb and the formation of digits in an posterior to anterior sequence in most land vertebrates.’
    • ‘Accordingly, the role of vertebral rotation in synapsid locomotion might be better investigated in terms of its effect on limb extension and recovery.’
    1. 4.1Ballet The ability of a dancer to raise one leg above their waist, especially to the side.
      ‘she has amazing extension’
      ‘he could perform 180-degree extensions’
      • ‘I have read your advice on extensions and there is one I have a problem with.’
      • ‘So instead of 180 degrees of extension per double push, he'll get 130 or 140, which is more than 90.’
      • ‘Remember that extension is strength and placement as well as flexibility.’
    2. 4.2Medicine 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.
      • ‘Posterior elbow pain in the setting of repetitive elbow extension suggests the diagnosis of triceps tendinosis.’
      • ‘The arm is immobilized in a cast with the elbow in extension, and x-rays are obtained.’
      • ‘Adolescents with spondylolysis or spondylolisthesis experience an exacerbation of lumbosacral pain with spinal extension.’
      • ‘When the digit has been brought to full extension, a fasciectomy is performed.’
      • ‘An evaluation for effusion should be conducted with the patient supine and the injured knee in extension.’
    3. 4.3 The lengthening of a horse's stride within a particular gait.
      • ‘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.’
  • 5as modifier Instruction by a university or college for students who do not attend full time.

    ‘extension courses’
    • ‘As the school's night college, the extension school attracts extraordinary students.’
    • ‘Additionally, the International Seminary of Miami is offering some extension courses.’
    • ‘Nearby colleges and universities may also offer extension classes.’
    • ‘We need to adjust our thinking to allow the faculty to provide quality advising, instruction, and extension outreach programs.’
    • ‘I checked with every extension office, university, and any other place I could think of; no one could tell me much about it.’
    • ‘Every university should have an extension department to promote students' participation in community-based activities.’
    • ‘Some large nurseries and most university extension services will do this for a nominal charge.’
    • ‘The Food Innovation Center, a branch of Oregon State University's agricultural extension service, is based in Portland.’
    • ‘Still barred were the hundreds of students who would have taken courses offered by the university's extension service, mostly English-language classes.’
    • ‘My wife went to extension classes at the University of North Carolina on post.’
    • ‘He went to the University of London (King's College) extension classes and later became an evening class teacher himself.’
    • ‘He also supported London and Oxford in setting up similar extension courses.’
    • ‘Rosenow took his concern to Carl Duley, University of Wisconsin county extension agent for Buffalo County.’
    • ‘The lack of opportunities for the higher education of women led to the founding of the university extension movement.’
    • ‘This was in the aftermath of the arrival of proper University extension classes established by the 1902 Education Act.’
    • ‘In Australia he worked initially as a bush labourer, then as a teacher, and after 1888 for the University of Sydney's extension classes.’
    • ‘In fact, there are no universities in Gambia, but in the late 1990s, university extension programs were offered for the first time.’
    • ‘What was once a small school now serves a wider population that includes adults and extension programs.’
    • ‘Contact Olds College extension services at 1-800-661-6537 for more information.’
    • ‘She was learning how to crochet, taking a class in it at the extension college.’
  • 6Logic
    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
    • ‘To make sure that the extension of the definiens matches that of the definiendum, Beardsley thinks, the second disjunct of the definition is needed.’
    • ‘All versions of externalism have in common that intensions don't determine extensions.’
    • ‘That is, a concept is indefinitely extensible if any attempt to delineate the extension of the concept leads to an instance of the concept not so delineated.’
    • ‘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.’
  • 7Physics Philosophy
    The property of occupying space; spatial magnitude.

    ‘nature, for Descartes, was pure extension in space’
    • ‘Space was the empty extension that allowed his bits of matter - his atoms - to move about.’
    • ‘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.’
    • ‘In particular, he believed that Descartes' identification of matter with extension, and therefore space, entails making it eternal and infinite.’
    • ‘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.’
    • ‘A point is an element that has position, but no extension.’


  • by extension

    • Taking the same line of argument further.

      ‘this raised serious questions about his credibility and, by extension, the credibility of the company’
      • ‘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.’
      • ‘So far the question of asylum seekers and, by extension, racism has been dealt with in a very piecemeal fashion by the Government.’
      • ‘That would be the boards of directors, and, by extension, the stockholders.’
      • ‘But from past experience, I doubt that any serious combat, and by extension deaths, will occur.’
      • ‘Well, primarily, it has been the Department of Education and, by extension, it has been the Government.’
      • ‘Suddenly the whole future of Woomera - and by extension of the whole remote detention system - is up in the air.’
      • ‘And by extension so are his attorneys when it comes to confidential information.’
      • ‘For if both of these apparently carefree images have a message, it is surely of the fleeting nature of such moments and, by extension, of life itself.’
      • ‘Only those who hold ministerial positions in government are accountable to Parliament and by extension the nation.’
      • ‘I wonder if, by extension, one could say that radical feminism will soon become a movement that died.’


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