What is called fan in Sanskrit language?

There isn't a single perfect Sanskrit word for "fan" in the modern sense of an appliance. However, depending on the context, you could use various words:

For a hand-held fan:

* पंख (panka): This is the most common word for "fan" in modern Hindi, and it is derived from Sanskrit.

* विस्तृत (vistṛta): This literally means "expanded" or "spread out" and could describe the action of a hand fan.

* वायु (vāyu): This means "air" and could be used to describe the action of a fan pushing air.

For an electric fan:

* वायु-यन्त्र (vāyu-yantr): This literally means "air machine" and could be used to describe an electric fan.

* विद्युत-पंख (vidyut-panka): This combines the words for "electricity" and "fan" and could be used to describe an electric fan.

Ultimately, the best word to use will depend on the specific context.