What are the main characteristics of the meridians?
Answer:
Answer by Student
 Meridians are imaginary lines that run northsouth on the Earth’s surface and measure the distance east or west of the prime meridian.
 The prime meridian is the reference line that passes through Greenwich, England, and divides the Earth into two equal halves: the Eastern Hemisphere and the Western Hemisphere.
 The lengths of the meridians are equal and each one is a semicircle that connects the North Pole and the South Pole.
 The distance between the meridians decreases as they move away from the equator towards the poles, where they converge at a point.
 There are 360 meridians of longitudes and the measure of the angular distance of the eastwest of the prime meridian is called the longitude.
Detailed Answer by Teachoo

Meridians are
imaginary lines
that run northsouth on the Earth’s surface and measure the distance east or west of the prime meridian. They are not visible on the Earth, but they are drawn on maps and globes to help us locate places and study the Earth’s geography.

The prime meridian is the
reference line
that passes through Greenwich, England, and divides the Earth into two equal halves: the Eastern Hemisphere and the Western Hemisphere. The prime meridian has a longitude of 0° and it is also called the Greenwich Meridian or Universal Time Meridian.

The lengths of the meridians are
equal
and each one is a semicircle that connects the North Pole and the South Pole. This is because they are halves of great circles that pass through the center of the Earth. The length of a meridian on a modern ellipsoid model of Earth (WGS 84) has been estimated as 20,003.93 km (12,429.87 mi).

The distance between the meridians
decreases
as they move away from the equator towards the poles, where they converge at a point. This is because they are arcs of circles that have different radii depending on their latitude. The distance between any two meridians at an interval of 1 degree varies from 111 kilometers at the equator to zero at the poles.
 There are 360 meridians of longitudes and the measure of the angular distance of the eastwest of the prime meridian is called the longitude. The longitude of a place can range from 0° to 180° east or west of the prime meridian. For example, Moscow has a longitude of 37.6°E, which means it is located 37.6° east of the prime meridian.