sidereal
UK: saɪˈdɪəriəl | US: saɪˈdɪriəl
adj. relating to the stars or constellations
adj. measured by the apparent motion of the stars
The word sidereal traces back to Latin sidereus, derived from sidus (star). It entered English in the early 17th century, primarily in astronomical contexts, to describe phenomena measured by stellar motion (e.g., sidereal day). The morpheme sider- appears in other star-related terms like sidereal time and consider (originally "to observe the stars for omens"). The suffix -eal reinforces its adjectival function, linking it to celestial observations.
A sidereal day is about 4 minutes shorter than a solar day.
Astronomers use sidereal time to track celestial objects.
The sidereal month measures the Moon's orbit relative to distant stars.
Ancient cultures relied on sidereal calendars for navigation.
The telescope's sidereal drive compensates for Earth's rotation.