Definitions of extension:

• noun:   act of expanding in scope; making more widely available

  Example: "Extension of the program to all in need"

• noun:   act of stretching or straightening out a flexed limb
• noun:   an educational opportunity provided by colleges and universities to people who not enrolled as regular students
• noun:   an additional telephone set that is connected to the same telephone line
• noun:   amount or degree or range to which something extends

  Example: "The wire has an extension of 50 feet"

• noun:   the ability to raise the working leg high in the air

  Example: "The dancer was praised for her uncanny extension"

• noun:   a string of characters beginning with a period and followed by one to three letters; the optional second part of a PC computer filename

  Example: "Most applications provide extensions for the files they create"

• noun:   a mutually agreed delay in the date set for the completion of a job or payment of a debt

  Example: "They applied for an extension of the loan"

• noun:   an addition to the length of something
• noun:   the spreading of something (a belief or practice) into new regions
• noun:   an addition that extends a main building
• noun:   the most direct or specific meaning of a word or expression; the class of objects that an expression refers to

  Example: "The extension of `satellite of Mars' is the set containing only Demos and Phobos"