# Unit

Unit may refer to:

## General measurement

* Unit of measurement, a definite magnitude of a physical quantity, defined and adopted by convention or by law
** International System of Units (SI), modern form of the metric system
** English units, historical units of measurement used in England up to 1824
** Unit of length

## Science and technology
### Physical sciences

* Natural unit, a physical unit of measurement
* Geological unit or rock unit, a volume of identifiable rock or ice
* Astronomical unit, a unit of length roughly between the Earth and the Sun

### Chemistry and medicine

* Equivalent (chemistry), a unit of measurement used in chemistry and biology
* Unit, a vessel or section of a chemical plant
* Blood unit, a measurement in blood transfusion
* Enzyme unit, a measurement of active enzyme in a sample
* International unit, a unit of measurement for nutrients and drugs

### Mathematics

* Unit number, the number 1
* Unit, identity element
* Unit (ring theory), an element that is invertible with respect to ring multiplication
* Unit, a tuple of length 0; an empty tuple
* Statistical unit, a data point on which statistical analysis is performed
* Unit angle, a full turn equal to an angle of 1
* Unit circle, a circle with a radius of length 1
* Unit cube, a cube with sides of length 1
* Unit fraction, a reciprocal of a positive integer
* Unit imaginary number, square root of negative 1 $({\sqrt {-1}})$
* Unit impulse, an impulse of height 1
* Unit interval, an interval of distance 1
* Unit matrix, a diagonal matrix such that all elements on the main diagonal are 1 and all the others are zero
* Unit round-off, an upper bound on the relative error due to rounding in floating point
* Unit set, a singleton, a set with exactly 1 element
* Unit sphere, a sphere with a radius of length 1
* Unit square, a square with sides of length 1
* Unit vector, a vector with length equal to 1
* Unit type, a type allowing only one value in type theory

### Computing

* Central processing unit, the electronic circuitry within a computer that carries out the instructions of a computer program
* GNU Units, a software program for unit conversion
* Rack unit, a unit of measure most commonly used to define the size of certain computing equipment
* Unit testing, a method by which individual units of source code are tested

## Business

* Stock keeping unit, a discrete inventory management construct
* Strategic business unit, a profit center which focuses on product offering and market segment
* Unit of account, a monetary unit of measurement
* Unit coin, a small coin or medallion (usually military), bearing an organization's insignia or emblem
* Work unit, the name given to a place of employment in the People's Republic of China
* Telephone card unit. When bought contains a certain amount of units, which make up their own currency for making telephone calls, that may not necessarily correspond to the monetary cost of the actual telephone card.

## Military

* Active service unit, the former Provisional Irish Republican Army cell
* Military unit, an homogeneous military organization whose administrative and command functions are self-contained
* Sayeret Matkal (The Unit), the Israeli special forces unit

## Arts and entertainment

* UNIT, a fictional military organization in the science fiction television series Doctor Who
* Unit of action, a discrete piece of action (or beat) in a theatrical presentation

### Music

* Unit (album), 1997 album by the Australian band Regurgitator
* The Units, a synthpunk band

### Television

* The Unit, an American television series
* The Unit: Idol Rebooting Project, South Korean reality TV survival show

## Other uses

* Unit of alcohol, a measure of the volume of pure ethanol in an alcoholic beverage
* Unit (housing), a self-contained suite of rooms within a set of similar dwellings
* Unit, course credit at a school or other educational institution
* Multiple unit, self-propelled train carriage capable of coupling other units of the same type
* Head unit, a component of a stereo system mounted inside of a vehicle
* Unit (Cristian Fleming) (born 1974), electronic musician based in New York City
* Unit (Norway), a government directorate