longitudinal
Americanadjective
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of or relating to longitude or length.
longitudinal measurement.
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extending in the direction of the length of a thing; running lengthwise.
a thin, longitudinal stripe.
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Zoology. pertaining to or extending along the long axis of the body, or the direction from front to back, or head to tail.
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pertaining to a research design or survey in which the same subjects are observed repeatedly over a period of time.
noun
adjective
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of or relating to longitude or length
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placed or extended lengthways Compare transverse
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psychol (of a study of behaviour) carried on over a protracted period of time
Other Word Forms
- longitudinally adverb
Etymology
Origin of longitudinal
1535–45; < Latin longitūdin- (stem of longitūdō; longitude ) + -al 1
Explanation
Use the adjective longitudinal to describe something that takes place over a long period of time, like a study of the lifetime eating habits of people who live on islands. Sociologists and other scientists use the word longitudinal when they're talking about long-term research. Geographers also describe things as longitudinal, but instead they mean something that relates to the east-west measurement across the Earth. When doctors use the word, it's in yet another way, describing muscles or other body parts that run lengthwise, rather than up-and-down. Longitudinal comes from the Latin word longitudo, "length or duration."
Vocabulary lists containing longitudinal
The Old Man and the Sea
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This Week in Words: Current Events Vocab for February 3–February 9, 2024
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Articles on Benefits of Technology
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
More longitudinal studies will be needed to build on the research, but could eventually lead to different tests and treatment options for men and women.
From MarketWatch • Apr. 13, 2026
A 2026 longitudinal study in the Journal of Public Health reached a similar conclusion.
From The Wall Street Journal • Mar. 27, 2026
ALFA-K was developed to solve this problem by using longitudinal, single-cell data to reconstruct how cancer cells move through chromosome states over time and which states are favored by evolution.
From Science Daily • Jan. 26, 2026
Marc was accepted into AllFTD, a longitudinal study that is the largest ever conducted for this disease.
From Los Angeles Times • Sep. 7, 2025
The 11highs and lows11 of sound waves and other longitudinal waves are arranged in the 11forward11 direction.
From "Understanding Basic Music Theory" by Catherine Schmidt-Jones and Russel Jones
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
