point particle

Examples of point particles: (counterclockwise from top left) point mass for Newton's law of universal gravitation, point particles to measure distance between two charged particles, simple pendulum (point mass attached to the end of a massless string), ideal gas particles devoid of interactions (no collisions, gravitational force, or Coulomb's force between particles)

A point particle, ideal particle or point-like particle (or pointlike particle) is an idealization used in physics. Its defining feature is negligible spatial extension or a body whose own rotation is irrelevant. A point particle is an appropriate representation of any object whenever its size, shape, and structure are irrelevant in a given context. For example, from far enough away, any finite-size object will look and behave as a point-like object. Point masses and point charges are two common cases. When a point particle has an additive property, such as mass or charge, it is often represented mathematically by a Dirac delta function. In classical mechanics there is usually no concept of rotation of point particles about their "center".