An Etymological Dictionary of Astronomy and Astrophysics
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1) The physical situation reached in a fluid when complete balance exists between the internal pressure at any point and the weight of the material above the point.
2) For a star, the balance between the inward → gravitational force and the outward gas pressure everywhere in the star. → hydrostatic equation. See also → hydrodynamic equilibrium.

→ hydrostatic; → equilibrium.

The state of a rigid body which is not moving at all. The conditions for static equilibrium are: 1) the sum of the external forces on the object must equal zero, and 2) the sum of the → torques must equal zero. See also → dynamic equilibrium and → mechanical equilibrium.

→ static; → equilibrium.