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longitude

/ˈlɒndʒɪtjuːd/

Angular east-west position on Earth or in space

From Proto-Indo-European, through Latin long (long).

noun
long
Latin
AI-inferred
longus
“long, extended; lasting”
Latin
Verified
longitūdō
“length, long duration; measured length”

from Latin longitudo "length, long duration,"

+1 more source
Old French
Verified
longitude
“length”

from Old French longitude

Middle English
Verified
longitude
“length,” later the east-west geographic measurement

from Old French longitude

Modern English
longitude

Picture a medieval scholar measuring the heavens with a brass instrument: latitude tells how far north or south, while longitude stretches sideways around the globe. The word began much more simply, as Latin longus, “long,” which is related to Germanic forms behind English long and ultimately to the Indo-European root *del-, “long.” Latin turned that adjective into longitūdō, literally “length” or “long duration,” and Old French passed longitude into Middle English in the late fourteenth century. The geographic sense became especially urgent at sea, where knowing east-west position could mean reaching a port—or vanishing into the ocean; King Charles II founded Greenwich’s Royal Observatory in 1675 specifically to help solve the longitude problem. In 1884, Greenwich became the reference point for the world’s prime meridian, so every degree of longitude is, in effect, another measured slice of “long” wrapped around Earth.

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