Dyarchy, also known as diarchy, was a political system implemented in British India under the Government of India Act of 1919. It aimed to introduce a limited form of self-government in the provinces by dividing the subjects delegated to the provinces into two categories.

Explanation:
- Introduction of Dyarchy: The principle of dyarchy was introduced as a part of the constitutional reforms in British India. It was a significant departure from the previous centralized system of governance and aimed to grant a certain degree of autonomy to the provinces.
- Two Categories of Subjects: Under the dyarchy system, the subjects delegated to the provinces were divided into two categories - reserved and transferred. The reserved subjects were under the direct control and administration of the Governor, who represented the British government. On the other hand, the transferred subjects were entrusted to the elected ministers responsible to the provincial legislature.
- Administration of Reserved Subjects: The reserved subjects included important areas such as law and order, finance, revenue, and administration. These subjects remained under the control of the Governor and were not within the purview of the elected ministers. The Governor, along with his Executive Council, had the authority to make decisions on these matters.
- Administration of Transferred Subjects: The transferred subjects comprised areas like education, public health, agriculture, local self-government, etc. The elected ministers were responsible for the administration and management of these subjects. They had the power to formulate policies, enact laws, and execute plans pertaining to these areas.
- Role of Governor and Ministers: The Governor, as the head of the province, exercised control over the reserved subjects and had the power to override the decisions of the ministers if deemed necessary. The ministers, on the other hand, were accountable to the provincial legislature and had the responsibility of managing the transferred subjects.
- Significance and Implementation: Dyarchy was implemented to introduce a limited form of self-government in the provinces. It aimed to provide Indians with some level of participation in the governance process while retaining ultimate control with the British government. However, the system had several limitations and was criticized for its inherent flaws, leading to further demands for more comprehensive political reforms.

Overall, the principle of dyarchy in Indian history refers to the division of the subjects delegated to the provinces into two categories - reserved and transferred. It aimed to introduce a limited form of self-government by granting certain powers to elected ministers while retaining control over important areas with the Governor.