1. a mutually agreed delay in the date set for the completion of a job or payment of a debt

- they applied for an extension of the loan

Definition categories: time, delay, hold, postponement, wait

2. act of expanding in scope; making more widely available

- extension of the program to all in need

Definition categories: act, enlargement, expansion

3. the spreading of something (a belief or practice) into new regions

Similar word(s): propagation

Definition categories: communication, airing, dissemination, spreading

4. an educational opportunity provided by colleges and universities to people who are not enrolled as regular students

Definition categories: act, didactics, education, instruction, pedagogy, teaching

5. act of stretching or straightening out a flexed limb

Definition categories: act, stretching

6. a string of characters beginning with a period and followed by one or more letters; the optional second part of a PC computer filename

- most applications provide extensions for the files they create

- most BASIC files use the filename extension .BAS

Definition categories: communication, string

7. the most direct or specific meaning of a word or expression; the class of objects that an expression refers to

- the extension of `satellite of Mars' is the set containing only Demos and Phobos

Similar word(s): denotation, reference

Definition categories: thought, meaning, substance

8. the ability to raise the working leg high in the air

- the dancer was praised for her uncanny extension

- good extension comes from a combination of training and native ability

Definition categories: attribute, property, dance

9. amount or degree or range to which something extends

- the wire has an extension of 50 feet

Similar word(s): lengthiness, prolongation

Definition categories: attribute, longness

10. an additional telephone set that is connected to the same telephone line

Definition categories: man–made, phone, telephone

11. an addition to the length of something

Similar word(s): elongation

Definition categories: man–made, addition, improver

12. an addition that extends a main building

Similar word(s): annex, annexe, wing

Definition categories: man–made, addition, improver

Sentences with extension as a noun:

- Files with the .txt extension usually contain text.

- a browser extension