# Units and Measurement

Label numeric quantities with physical dimensions to allow locale-aware formatting and conversion between related units.

## Topics

### First Steps

`NSMeasurement`

A numeric quantity labeled with a unit of measure, with support for unit conversion and unit-aware calculations.

`NSUnit`

An abstract class representing a unit of measure.

`NSDimension`

An abstract class representing a dimensional unit of measure.

### Conversion

`NSUnitConverter`

An abstract class that provides a description of how to convert a unit to and from the base unit of its dimension.

`NSUnitConverterLinear`

A description of how to convert between units using a linear equation.

### Physical Dimension

`NSUnitArea`

A unit of measure for area.

`NSUnitLength`

A unit of measure for length.

`NSUnitVolume`

A unit of measure for volume.

`NSUnitAngle`

A unit of measure for rotation.

### Mass, Weight, and Force

`NSUnitMass`

A unit of measure for mass.

`NSUnitPressure`

A unit of measure for pressure.

### Time and Motion

`NSUnitAcceleration`

A unit of measure for acceleration.

`NSUnitDuration`

A unit of measure for duration of time.

`NSUnitFrequency`

A unit of measure for frequency.

`NSUnitSpeed`

A unit of measure for speed.

### Energy, Heat, and Light

`NSUnitEnergy`

A unit of measure for energy.

`NSUnitPower`

A unit of measure for power.

`NSUnitTemperature`

A unit of measure for temperature.

`NSUnitIlluminance`

A unit of measure for luminance.

### Electricity

`NSUnitElectricCharge`

A unit of measure for electric charge.

`NSUnitElectricCurrent`

A unit of measure for electric current.

`NSUnitElectricPotentialDifference`

A unit of measure for electric potential difference.

`NSUnitElectricResistance`

A unit of measure for electric resistance.

### Concentration and Dispersion

`NSUnitConcentrationMass`

A unit of measure for concentration of mass.

`NSUnitDispersion`

A unit of measure for an amount-of-substance fraction.

### Fuel Efficiency

`NSUnitFuelEfficiency`

A unit of measure for fuel efficiency.

### Fundamentals

Numbers, Data, and Basic Values

Work with primitive values and other fundamental types used throughout Cocoa.

Strings and Text

Create and process strings of Unicode characters, use regular expressions to find patterns, and perform natural language analysis of text.

Collections

Use arrays, dictionaries, sets, and specialized collections to store and iterate groups of objects or values.

Dates and Times

Compare dates and times, and perform calendar and time zone calculations.

Data Formatting

Convert numbers, dates, measurements, and other values to and from locale-aware string representations.

Filters and Sorting

Use predicates, expressions, and sort descriptors to examine elements in collections and other services.