ex·​ten·​sion | \ ik-ˈsten(t)-shən How to pronounce extension (audio) \

Definition of extension

1a : the action of extending : state of being extended
b : an enlargement in scope or operation tools are extensions of human hands
2a : the total range over which something extends : compass
3a : the stretching of a fractured or dislocated limb so as to restore it to its natural position
b : an unbending movement around a joint in a limb (such as the knee or elbow) that increases the angle between the bones of the limb at the joint — compare flexion sense 4a
4 : a property whereby something occupies space
5 : an increase in length of time specifically : an increase in time allowed under agreement or concession
6 : a program that geographically extends the educational resources of an institution by special arrangements (such as correspondence courses) to persons otherwise unable to take advantage of such resources
7a : a part constituting an addition
b : a section or line segment forming an additional length
c : an extra telephone connected to the principal line
d : a length of natural or synthetic hair that is worn attached to one's natural hair
e : a series of usually three or four characters following a dot at the end of the name of a computer file that specifies the file's format or purpose
8 : a mathematical set (such as a field or group) that includes a given and similar set as a subset

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Examples of extension in a Sentence

extension of the patient's life He's asking for a contract extension. Make sure that the muscles get the proper amount of extension. I missed the deadline but was granted an extension.
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Recent Examples on the Web

Also under construction are a 10-mile extension of the 95 Express Lanes to Frederick, and the addition of 22.5 miles of HOT lanes on I-66 outside the Capital Beltway to Gainesville in Prince William County. Washington Post, "395 Express Lanes on track to open in November," 14 Sep. 2019 Kriske said the extension would continue to strengthen and increase ridership on the line by connecting Burbank to a Metro light-rail hub. Anthony Clark Carpio, Burbank Leader, "Officials put brakes on BurbankBus Gold Route, steer toward other changes," 13 Sep. 2019 Previous measures helped pay for the fourth bore through the Caldecott Tunnel, carpool lanes on I-680; $360 million went toward city streets and maintenance and improvement, the eBART extension and widening of Highway 4. Gary Richards, The Mercury News, "Not another transportation sales tax: Roadshow," 11 Sep. 2019 The contract extension will keep Jones from becoming an unrestricted free agent after the 2019 season and ties him to the Patriots through the 2022 season. Mark Inabinett | Minabinett@al.com, al, "New England Patriots lock up Jonathan Jones with new contract," 7 Sep. 2019 Adding a space specialty to the TPS program seems like a natural extension, but establishing a specialist school represents a cultural shift for the storied organization. Joe Pappalardo, Popular Mechanics, "The Air Force's Most Famous Pilot School Is Going To Space," 3 Sep. 2019 For Plantyful Sweets owner Gaby Borrego, the popularity of CBD is a natural extension of the current attention being paid to anti-inflammatory and plant-based diets. Paul Stephen, ExpressNews.com, "San Antonio food pros catch CBD wave for big biz buzz," 24 Aug. 2019 Earlier in the year, the couple gave us a major fitness and food challenge, so this is a natural extension of their work. Katherine J Igoe, Marie Claire, "Now You'll Be Able to Train with J. Lo and A. Rod, Thanks to a New App Partnership," 22 Aug. 2019 For Michael Shaw, a 45-year-old car dealer in Denver, buying an Inspirato Pass was a natural extension of his regular Inspirato membership, which he's had for five years. Claire Ballentine, chicagotribune.com, "Subscription model comes to luxury travel," 20 Aug. 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'extension.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of extension

15th century, in the meaning defined at sense 1a

History and Etymology for extension

Middle English, from Late Latin extension-, extensio, from Latin extendere

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Statistics for extension

Last Updated

8 Oct 2019

Look-up Popularity

Time Traveler for extension

The first known use of extension was in the 15th century

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More Definitions for extension



English Language Learners Definition of extension

: the act of making something longer or greater
: the act of straightening or stretching something (such as an arm or a leg)
: extra time allowed for doing something


ex·​ten·​sion | \ ik-ˈsten-shən How to pronounce extension (audio) \

Kids Definition of extension

1 : the act of making something longer or greater extension of the sail
2 : an increase in length or time
3 : a part forming an addition or enlargement


ex·​ten·​sion | \ ik-ˈsten-chən How to pronounce extension (audio) \

Medical Definition of extension

1 : the stretching of a fractured or dislocated limb so as to restore it to its natural position
2 : an unbending movement around a joint in a limb (as the knee or elbow) that increases the angle between the bones of the limb at the joint — compare flexion sense 1

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Legal Definition of extension

: an increase in length of time specifically : an increase in the time allowed under an agreement

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Comments on extension

What made you want to look up extension? Please tell us where you read or heard it (including the quote, if possible).


a topic to which one constantly reverts

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