point source

1. With respect to radiation, a single point in space emitting radiation.

The radiation from such a source may be expressed as flux per unit solid angle (W sr^-1).

1. In experimental studies of atmospheric turbulence and diffusion, a source of particulate matter from a single fixed point.
   There are continuous and instantaneous point sources. The analogous concepts of line source and plane source are also frequently encountered.
   
2. In hydrodynamics, a source of mass, that is, a singular point in the field where the equation of continuity fails.