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
Etymology
Origin of longitudinal
1535–45; < Latin longitūdin- (stem of longitūdō; see 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.
Although we had decades of clinical data validating its effectiveness, it was an observation from a longitudinal study of healthy nurses in the 1980s that spurred the largest bump in hormone usage.
From MarketWatch • May 12, 2026
A 2026 longitudinal study in the Journal of Public Health reached a similar conclusion.
From The Wall Street Journal • Mar. 27, 2026
A longitudinal study involves repeatedly collecting data from the same group over an extended period, tracking changes and trends over a period of time.
From Science Daily • Dec. 10, 2025
Lewis, the Measure of America director, pointed to a longitudinal study of young people in similar situations.
From Los Angeles Times • Nov. 9, 2025
The effects of musical training on structural brain development: A longitudinal study.
From "Music and the Child" by Natalie Sarrazin
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.
