Which of these terms describes the measurement of a star's distance from Earth based on parallax?

The term that describes the measurement of a star's distance from Earth based on parallax is the parsec. Parallax is the apparent shift in position of an object when viewed from different angles, and in astrophysics, it refers to the way nearby stars appear to move against the background of more distant stars as the Earth orbits the Sun. By measuring this angular shift, astronomers can calculate the distance to the star using trigonometry.

One parsec is defined as the distance at which one astronomical unit (the average distance from Earth to the Sun) subtends an angle of one arcsecond. This measurement method is particularly effective for stars within a few hundred light-years from Earth, as the angles involved are small and can be accurately measured.

In the context of the other terms: absolute magnitude refers to the intrinsic brightness of a star as seen from a standard distance; light-year is a measure of distance based on how far light travels in one year, and apparent magnitude describes how bright a star appears from Earth without regard to its distance. While these terms are related to stars and their properties, they do not specifically pertain to the measurement of distance using parallax, making parsec the correct term.