Equator is to latitude as Prime Meridian is to longitude.

Explanation:
The Equator is an imaginary line that divides the Earth into the Northern Hemisphere and the Southern Hemisphere. It is a line of latitude, which measures the distance north or south of the Equator. The Equator is located at 0 degrees latitude.

Similarly, the Prime Meridian is an imaginary line that divides the Earth into the Eastern Hemisphere and the Western Hemisphere. It is a line of longitude, which measures the distance east or west of the Prime Meridian. The Prime Meridian is located at 0 degrees longitude.

Key Points:
- The Equator is a line of latitude, while the Prime Meridian is a line of longitude.
- Latitude measures distance north or south of the Equator, while longitude measures distance east or west of the Prime Meridian.
- The Equator is located at 0 degrees latitude, while the Prime Meridian is located at 0 degrees longitude.
- Latitude and longitude are used together to determine specific locations on Earth's surface.
- Latitude and longitude are measured in degrees, with 90 degrees being the maximum for both latitude and longitude.

Conclusion:
In summary, the Equator is to latitude as the Prime Meridian is to longitude. These lines help us locate specific points on Earth's surface and divide the Earth into different hemispheres. Understanding latitude and longitude is essential for navigation and understanding global coordinates.