What does meridian mean?
A meridian is most commonly a line of longitude: an imaginary great circle running from pole to pole and used together with latitude to describe a position on Earth. The prime meridian, conventionally passing through Greenwich, is the reference for measuring longitude. In formal figurative writing, a meridian is the highest point or culmination of a life, career, or achievement. Astronomy uses the term for a great circle that passes through the celestial poles and the observer's zenith, allowing the timing of a star's culmination. The word can also function as an adjective in technical phrases such as “meridian altitude” and “meridian circle.” Its history comes through Latin, where meridianus referred to midday and, by extension, the south-facing position of the Sun. The modern sense concerning lines of longitude developed from the idea of a line passing through the highest point of the sky.
A great circle passing through the Earth's poles, used to specify longitude; the highest point or culmination of something; or, in astronomy, a great circle passing through the poles and the observer's zenith.
"The team celebrated at the meridian of the project's success."
The geographical and astronomical senses are technical, while the figurative sense is formal and literary.
Relating to a meridian, especially a line of longitude or a great circle through the observer's zenith.
"The observers recorded the meridian altitude of the star."
Primarily used in navigation, astronomy, surveying, and related technical writing.
Used when referring to multiple longitude lines, astronomical circles, or points of culmination.
"The atlas shows the major meridians at ten-degree intervals."
The prime meridian at Greenwich gives the world its familiar zero line, separating eastern and western longitude.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does meridian come from?
The English word comes from Latin meridianus, “pertaining to noon or the south,” from meridiēs, meaning “midday” or “noon.” The Latin term also came to refer to the meridian line, the semicircle passing through the poles and the point of the Sun's greatest height. The modern geographic and astronomical senses developed from that astronomical and geographical usage.
Related word forms
How meridian is actually used
The geographical sense is standard in navigation, cartography, astronomy, and surveying. The figurative sense is formal and often suggests the highest point of a life, career, or period. As an adjective, it is usually used in technical contexts, especially astronomy and navigation.
Easily confused with meridian
A meridian is a line of longitude or a point of culmination, whereas a median is a middle value or line in an ordered group or geometric figure.