It's "axis" is probably the answer, but the question doesn't make complete sense.
The axis
the equator is the imaginary line around the earth.
The equator is an imaginary line which indicates where the middle of the earth is and it goes around.
The imaginary line between the poles of the Earth around which the Earth spins is called the "axis of rotation".
Anything that rotates has an imaginary line that it appears to rotate around, and that's what's called the "axis". Since the sun definitely rotates, there's an imaginary line through it that it seems to rotate around, and it's completely proper to refer to that imaginary line as the sun's axis.
Its axis The earth rotates around its axis - an imaginary line running from the North Pole through the centre of the earth to the South Pole. It rotates around this line once every day. it is this rotation which causes day and night. axis
That refers to the imaginary line, from the north pole to the south pole, around which Earth rotates.That refers to the imaginary line, from the north pole to the south pole, around which Earth rotates.That refers to the imaginary line, from the north pole to the south pole, around which Earth rotates.That refers to the imaginary line, from the north pole to the south pole, around which Earth rotates.
The imaginary line between the poles of the Earth around which the Earth spins is called the "axis of rotation".
axis
The equator
the equator.
The line your referring to is the Equator.