A threshold is a fixed location or value where an abrupt change is observed.

• In architecture, a threshold is a strip of wood, metal or stone located on the floor in a doorway following the line of division between the two spaces linked by the doorway.

• In telecommunication, the term threshold has the following meanings:
  1. The minimum value of a signal that can be detected by the system or sensor under consideration.
  2. A value used to denote predetermined levels, such as those pertaining to volume of message storage, i.e., in-transit storage or queue storage, used in a message switching center.
  3. The minimum value of the parameter used to activate a device.
  4. The minimum value a stimulus may have to create a desired effect.
  • Source: from Federal Standard 1037C and from MIL-STD-188

• In electrical engineering and machine learning, a threshold circuit or unit is a one-input, one-output device or object that implements a Heaviside step function; the threshold value corresponds to the transition in this function between one and zero.

• In elections, threshold refers to the minimal amount of votes necessary to win representation.

• Name of progressive metal band Threshold from England.

• In occupational safety and health, see ACGI and its Threshold Limit Values (TLV).

• In the video game "Halo", the planet around which the ringworld Halo orbits. It is presumably a gas giant, as there is a level in Halo 2 set in a research facility which is suspended in the atmosphere of Threshold and falls a great distance into the atmosphere later in that mission without ever hitting land. Threshold has one known natural satellite, a moon named Basis.

A literal meaning of the term threshold, is "that which holds thresh", and the word derives from the practise, in antiquity, in certain types of dwelling in England, to lay straw (or "thresh") down on an earth floor to provide a relatively warm and clean floor. The threshold was a strip of wood at the doorway which prevented thresh from migrating through the doorway as it was used by the occupants of the dwelling.