A more thorough explanation:

Definition: A form of government where two people share the ruling power.

For example, William and Mary of England ruled together as a diarchy. Another example is the Roman principate, where sovereignty was shared between the princes and the senate.

In India, diarchy was introduced as a constitutional reform in 1919. It divided the provincial executives into two sections: authoritarian and popularly responsible. The authoritarian section was composed of councillors appointed by the Crown, while the popularly responsible section was composed of ministers appointed by the governor and responsible to the provincial legislative councils. This system ended when full provincial autonomy was granted in 1935.

The examples illustrate how diarchy is a form of government where power is shared between two individuals or groups. It can be seen as a way to balance power and prevent one person or group from having too much control.