1. The angular displacement undergone by the position of a star when observed from two different points.
2. The change in the apparent position of an object against its background when viewed from two different positions.

In astronomy, nearby stars show a shift owing to parallax when viewed from different positions on the earth's orbit around the sun. A star's parallax is used to determine its distance from the earth.

Nearer bodies, such as, the moon, sun, and planets also show a parallax caused by the motion of the earth.

The change in an astronomical object's apparent position caused by the change in the observer's position because of the motion or rotation of the earth during a day.