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

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.
Recent Examples on the Web The pilot home delivery program is an extension of that service. Diane Bellcolumnist, San Diego Union-Tribune, 12 May 2022 The Cannes Film Festival deal, under which TikTok is paying for its sponsorship position, is an extension of that work, according to Waterworth. Todd Spangler, Variety, 11 May 2022 Gamification is an extension of what younger customers experience in the nonfinancial parts of their lives, including in entertainment and education, said Mike Foy, head of wealth intelligence at market-research firm J.D. Power. Suman Bhattacharyya, WSJ, 10 May 2022 The former living area is now an extension of the modest dining room, which can seat up to 14 and is decorated with family photos and books from the couple’s own residence. New York Times, 10 May 2022 Being an extension of the Bored Ape ecosystem, Otherdeed NFTs were seen as an opportunity to further the project’s value. Taylor Locke, Fortune, 6 May 2022 Sleeping in groups, predator threats or not, is also a natural extension of the way that people in small-scale societies live during the day, Yetish says. Elizabeth Preston, Smithsonian Magazine, 6 May 2022 Your product pages are an extension of the digital sales journey; make sure to leverage them. Steve Ohanians, Forbes, 4 May 2022 The most immediate impact on drivers would be the extension of the suspension of the state’s 25-cents-per-gallon gasoline tax until Dec. 31. Christopher Keating, Hartford Courant, 27 Apr. 2022 See More

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.

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

Buying Guide

Our Reviews team has selected the best resistance bands.

Learn More About extension

Time Traveler for extension

Time Traveler

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

See more words from the same century

Dictionary Entries Near extension



extension agent

See More Nearby Entries 

Statistics for extension

Last Updated

15 May 2022

Cite this Entry

“Extension.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/extension. Accessed 24 May. 2022.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

More Definitions for extension


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



Legal Definition of extension

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

More from Merriam-Webster on extension

Nglish: Translation of extension for Spanish Speakers

Britannica English: Translation of extension for Arabic Speakers

Britannica.com: Encyclopedia article about extension


Test Your Vocabulary

Name That Color

  • a light greenish blue color
  • Name that color:
True or False

Test your knowledge - and maybe learn something along the way.

Universal Daily Crossword

A daily challenge for crossword fanatics.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!