Your thinking of the Prime Meridian, which terminates at the poles, and which connects to the International Date Line -- a non-straight line for political reasons, that essentially mirrors the PM, pole to pole.
meridians
Latitude and longtitide are used to indicated the fixed location of a point or sphere in relation to two of that sphere's opposite poles and one line joining them. Here on Earth the two poles are the North Pole and the South Pole, and the line joining them is the one which runs through London, England. Latitide and longitude do not apply to a planet, as it orbits the Sun and is always moving.
A meridian describes an arc connecting the north and south poles (a single line of longitude). As such, a meridian will be 180 degrees.
A line of longitude may also be known as a meridian.Meridians (lines of Longitude) are great circles that go round the Earth through the North and South Poles. So they represent one-half of a polar circumference of the planet.The Prime Meridian runs through England (Greenwich) and is 0 degrees longitude.
The Line of Demarcation split South America into sections for the countries which claimed it. The Line of Demarcation was drawn by Pope Alexander in 1493.
Axis
The axis
meridians
True meridian through a point is the line in which a plane, passing that point and the north and south poles, intersects with surface of the earth. It thus, passes through the true north and south. the direction of true meridian through a point can be established by astronomical observations.
axis - An imaginary line that passes through earths center and its north and south poles.
The North and South Poles are indeed imaginary points on the Earths surface where the line of the axis of it's spin would pass through.
There is no begining or end. It is a line that goes on forever passing thru the north and south poles.
The straight line between the poles is the Earth's axis of rotation. The curved lines between the poles and along the surface are the meridians of longitude.
The axis is the imaginary line that a planet rotates about, The earth's axis passes through the North and South poles.
A line running north and south/ up and down is called a vertical line.
equator
A geodesic line connecting the north and south poles.