Also known as an ideal particle , a point particle is an idealization of classical physics according to which the size, shape, and structure of an object are irrelevant as long as its context allows. In terms of mass, this means that the object in question is thought of or modeled as an infinitesimal element, one that is infinitely small in volume.
For example, despite occupying a volume, elementary particles are usually considered point particles when put in relation to complex particles; this is because elementary particles have no known internal structure.