Which type of line on Earth runs horizontally?

The correct answer is latitude, which represents lines that run horizontally around the Earth. These lines are parallel to the Equator and measure the distance north or south of it, with the Equator designated as 0 degrees latitude.

Latitude lines provide important reference points for navigation, climate, and mapping. For instance, as you move north or south from the Equator, the latitude values increase up to 90 degrees at the poles.

In contrast, meridians and longitude lines run vertically from pole to pole, measuring the distance east or west of the Prime Meridian. The term "Equator" specifically refers to the zero-degree latitude line, but it is just one of the many lines of latitude, which collectively are the emphasis of this question.