The equator is the best known such imaginary line. However, latitudes (including the Arctic Circle) are also imaginary lines encircling the earth as are longitudes.
the equator
Equator
An imaginary straight line around which an object like Earth rotates is called its axis. Earth's axis is an imaginary line that runs from the North Pole to the South Pole, around which the planet rotates as it orbits the Sun.
There is no such line. The imaginary line through its centre is the axis, which the Earth rotates around; the imaginary line an equal distance from the poles is the equator. Neither make it spin - that is caused by momentum from the planet's formation.
Equator
The equator runs around the center of the earth.
Earth spins around an imaginary line called its axis. The axis runs from the North Pole to the South Pole, and the rotation of the Earth on this axis is what causes day and night.
the equator
The horizontal line that goes around the "waist" of the Earth is the Equator. The vertical line that goes vertically around the Earth, through the poles, is the Prime Meridian.
The imaginary line around which the Earth appears to be turning is called the Earth's axis. It runs from the North Pole to the South Pole and is tilted at an angle of approximately 23.5 degrees relative to its orbit around the Sun.
The imaginary line that the Earth rotates around is called its axis. It runs from the North Pole to the South Pole and is tilted at an angle of approximately 23.5 degrees. This tilt is what causes the changing seasons on Earth.
The celestial equator is the imaginary line in the heavens that runs around the Earth midway between the celestial poles. It is an extension of Earth's equator onto the celestial sphere and divides the sky into northern and southern hemispheres.