Which term describes the great circle on the celestial sphere representing the sun's apparent path?

The term that describes the great circle on the celestial sphere representing the sun's apparent path is the ecliptic. This is a crucial concept in both astronomy and navigation, as the ecliptic represents the plane of Earth's orbit around the sun, which projects onto the celestial sphere.

As the Earth orbits, the sun appears to move along this path throughout the year, which is observed as the changing positions of the sun against the background of stars. The ecliptic is not just significant for understanding the sun's motion; it also serves as a reference for the celestial coordinate system. It's where the zodiac constellations are located, and it influences the apparent motion of other celestial bodies relative to Earth.

While the celestial meridian relates to the vertical circle that connects the zenith to the north and south points, and the equator is an imaginary line that divides the celestial sphere into northern and southern hemispheres, these do not describe the sun's path. The celestial horizon, on the other hand, represents the line around the observer's point of view, which also doesn't depict the sun's apparent trajectory in the sky. Thus, the ecliptic stands out as the correct choice in defining the sun's apparent path across the celestial sphere.