Definition

1. Proper Noun:
   • The zero-degree line of longitude: The "prime meridian" is the imaginary north-south line on the Earth's surface, defined as having a longitude of 0 degrees. It serves as the universal reference point from which all other longitudes (east and west) are measured. By international convention, it passes through the Royal Observatory in Greenwich, London, England.

Usage

• The "prime meridian" is used as a singular, proper noun, often capitalized. It is the fundamental reference line for the global coordinate system of latitude and longitude.
• It is used to calculate time zones, as Greenwich Mean Time (GMT) and Coordinated Universal Time (UTC) are based on the prime meridian.
• It divides the Earth into the Eastern and Western Hemispheres.

Examples

• Proper Noun:
  • All maps and navigation systems use the prime meridian as the starting point for measuring longitude.
  • The conference established the Greenwich Prime Meridian as the international standard in 1884.
  • When you cross the prime meridian, your longitude reading changes from east to west or vice versa.

Advanced Usage

• "The Greenwich Meridian": This is a direct synonym for the prime meridian, specifically naming its location. Example:
• "The zero meridian": A more technical term emphasizing its longitudinal value. Example:

Variants and Related Words

• Meridian (n): Any imaginary great circle on the Earth's surface passing through the North and South Poles. The prime meridian is the principal meridian.
• Longitude (n): The angular distance east or west of the prime meridian.
• Antimeridian (n): The meridian of 180° longitude, directly opposite the prime meridian, which largely serves as the International Date Line.

Synonyms

• Greenwich Meridian: The specific name for the prime meridian.
• Zero Meridian: Emphasizes its longitudinal coordinate.
• Initial Meridian: A less common term highlighting its role as the starting reference.

Related Phrases

• "East of the prime meridian": Describes locations with positive east longitude values.
  • Tokyo is located far east of the prime meridian.
• "West of the prime meridian": Describes locations with positive west longitude values.
  • New York is located west of the prime meridian.

Noun

1. meridian at zero degree longitude from which east and west are reckoned (usually the Greenwich longitude in England)