Paramanu is a technical term in Hinduism. It is defined as the smallest and indivisible particle of matter. In Hindi and Bengali language paramanu refers to the atom.
In Jainism it is one of the two types of Pudgala (matter), the other being Skandha. It also helps to define smallest measure of space. All the Parmanus occupy exactly same amount of space. The measure of the space occupied by one Parmanu is called Pradesha.