ex·​ten·​sion | \ik-ˈsten(t)-shən \

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

b : denotation sense 4

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

My signature nails: roughly $2,700 a year My nails feel like a true extension of myself. Bri Luna, Glamour, "I'm a Real Witch, and I Spend $7,855 a Year on My Beauty Rituals," 31 Oct. 2018 Last week’s late-breaking news that the Frick would be taking over the lease on Marcel Breuer’s Brutalist icon—which has been occupied by an extension of the Metropolitan Museum since 2016—was a real plot twist. Kelsey Keith, Curbed, "The inaugural monthly column from Curbed’s editor-in-chief turns an eye to Postmodernism, following the loss of Robert Venturi," 24 Sep. 2018 The installation also feels like an extension of the complex, cross-cultural conversation going on downstairs, inside a museum packed with 5,000 years of art history. New York Times, "23 Art Exhibitions to View in N.Y.C. This Weekend," 12 July 2018 The Harris County Houston Sports Authority on Monday unanimously approved an extension through 2050 on the club's lease at the downtown, 18-year-old stadium. Chandler Rome, Houston Chronicle, "Astros have plans for future improvements to Minute Maid Park," 10 July 2018 Dragic likely will not be part of the Heat's next incarnation and there is question about offering Winslow an extension. Ira Winderman, Sun-Sentinel.com, "ASK IRA: Should Heat offer anything and everything for Kawhi?," 6 July 2018 Hours before a hearing in San Diego, the Justice Department filed papers seeking an extension of the deadline, which is July 10 for all parents with children under 5 and July 26 to reunite everyone else. Time, "Trump Administration Wants More Time to Reunite Families Separated at the Border," 6 July 2018 By making Elastigirl no more than an extension of her family, Incredibles 2 regresses to a time when any power women managed to acquire was carefully controlled so as not constitute a threat to the male order. Andrea Thompson, Chicago Reader, "Incredibles 2 : Who’s afraid of the superpowered woman?," 29 June 2018 Most people don't have magically long blonde hair, but thankfully there are hair extensions to pull off the princess's trademark style. Blake Bakkila, Good Housekeeping, "These 3 DIY Disney Couples Costumes Are Perfect (and Easy!) for Halloween," 25 Oct. 2018

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

17 Dec 2018

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


ex·​ten·​sion | \ik-ˈsten-shən \

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 \

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



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 knickknack or trinket

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