Principal Secretary to the Prime Minister of India
The Principal Secretary to the Prime Minister of India (PS to the PM; ISO: Bhārat Ke Pradhānmantrī Ke Pradhān Saciv) is the administrative head of the Prime Minister's Office. The officeholder is generally a retired civil servant, commonly from the Indian Administrative Service and occasionally from the Indian Foreign Service.
Source: Wikipedia — Principal Secretary to the Prime Minister of India (CC BY-SA 4.0)