Enamel extension in dentistry

Extension of universal health care.

Extension (community development), the building of community capacity by outsiders, for instance, agricultural extension

Extension, the classical name for the Mc1r gene.

Extension (geology)

Extension, BC is a small former coal-mining village near Nanaimo, BC, Canada

Filename extension, a suffix to the name of a computer file applied to show its format

Hair extensions, strands of hair added to supplement a person's existing hair

Extension (semantics), the set of things to which a property applied

Extension cable

Eyelash extensions

Extension (music), a set of notes that fit outside the standard range

Tension (physics)

Extension (telephone), an internal telephone line attached to a PBX or Centrex system

Extension (metaphysics), the property of taking up space

Extension (computing), a computer program that is not useful in its own right but designed to be incorporated in another piece of software

Extension (mathematics); an extension of some structure is another structure which contains the original structure

Extension (kinesiology), a movement of a joint in which one part of the body is moved away from another.

System Extension, a particular type of this software on the classic Mac OS

Extension (Mozilla), this type of software for Firefox and other Mozilla projects

Extension school, a school for continuing education

Extensions the 1979 album by The Manhattan Transfer