extension

noun

ex·​ten·​sion ik-ˈsten(t)-shən 

1

a

: the action of extending : state of being extended

extension of the patient's life

b

: an enlargement in scope or operation

Tools are extensions of human hands.

2

a

: the total range over which something extends : compass

b

: denotation sense 4

3

a

: 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

I missed the deadline but was given an extension.

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

7

a

: 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

Synonyms of extension

• stretching
• prolongation

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 plan, which Democrats characterized as a good-faith offer to Republicans, would codify a one-year extension of health care subsidies that are set to expire at the start of 2026, raising premiums for millions of Americans. —Zachary Schermele, USA Today, 7 Nov. 2025

Automatic 5-year contract extensions, and four years' notice for contract termination. —Keith Matheny, Freep.com, 7 Nov. 2025

Xicoia is really an extension into the AI universe and AI world. —Diana Lodderhose, Deadline, 7 Nov. 2025

From extension removal to a preliminary cut and a few rounds of color, the transformation took a total of four days to complete with the help of celebrity colorist Jacob Schwartz. —Kaleigh Werner, Footwear News, 7 Nov. 2025

Word History

Etymology

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

First Known Use

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

Phrases Containing extension

• extension agent
• extension cord
• extension lead

Rhymes for extension

• attention
• contention
• convention
• declension
• detention
• dimension
• dissension
• distension
• intension
• invention
• laurentian
• prehension

Kids Definition

extension

noun

ex·​ten·​sion ik-ˈsten-chən 

1

: the act of extending : the state of being extended

2

: an increase in time

was given an extension to finish his project

3

: education by special programs at a distance from a school

4

a

: a part forming an addition or increase

b

: an extra telephone connected to the main line

Medical Definition

extension

noun

ex·​ten·​sion ik-ˈsten-chən 

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

extension

noun

ex·​ten·​sion

: an increase in length of time

specifically : an increase in the time allowed under an agreement