A collision between bodies in which part of their kinetic energy is transformed to another form of energy, tending to result in the slowing or joining together of the bodies.
A collision process whereby part of the total kinetic energy of the system is converted into a different form of energy, such as radiant energy.
A collision between bodies in which the total kinetic energy of the bodies is not conserved. In an inelastic collision, the total momentum of the two bodies remains the same, but some of the initial kinetic energy is transformed into heat energy internal to the bodies, used up in deforming the bodies, or radiated away in some other fashion. Inelastic collisions, such as the collision of two balls of clay, tend to result in the slowing and sometimes the joining together of the colliding bodies.