Ecliptic

The great circle on the celestial sphere traced by the Sun's apparent path through the year — in effect the plane of Earth's orbit projected onto the sky. The band of the zodiac straddles it, and the Moon and planets are never found far from it, which is why the old astronomers treated it as the highway of the wandering stars.

From Greek ekleiptikē (grammē), 'line of eclipses' — eclipses occur only when the Moon crosses this line, where the paths of Sun and Moon meet.