longitudinal
adjective
lon·gi·tu·di·nal
ˌlän-jə-ˈtüd-nəl 
-ˈtyüd-,
-ˈt(y)ü-dᵊn-əl,
British also ˌläŋ-gə-
1
: placed or running lengthwise
The insect's back is black with yellow longitudinal stripes.
2
: of or relating to length or the lengthwise dimension
the longitudinal extent of the building
3
: involving the repeated observation or examination of a set of subjects over time with respect to one or more study variables
a longitudinal study of juvenile offenders over a period of five years
longitudinally
adverb
Examples of longitudinal in a Sentence
The insect's body is black with yellow longitudinal stripes.
calculating the longitudinal position of a ship
a longitudinal study of career aspirations among girls from 5 to 17
Recent Examples on the Web
However, further longitudinal studies are necessary to confirm these findings.
—
New Atlas, 28 July 2025
Researchers affiliated with Harvard Business School recently conducted a decade-long longitudinal study on retirement behavior—tracking 14 individuals closely over ten years and surveying 106 more—revealing comparative insights into different retirement transition approaches.
—Wes Moss, Forbes.com, 22 July 2025
Genetic and environmental influences on sleep quality, ability to settle, and crying duration in 2- and 5-month-old infants: A longitudinal twin study.
—Daniella Gray, MSNBC Newsweek, 8 July 2025
Likewise, the background blur is very clean and free of color fringing (longitudinal chromatic aberration) in the fall off between focus and blur.
—PC Magazine, 8 June 2025
See All Example Sentences for longitudinal
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New Atlas, 28 July 2025
Researchers affiliated with Harvard Business School recently conducted a decade-long longitudinal study on retirement behavior—tracking 14 individuals closely over ten years and surveying 106 more—revealing comparative insights into different retirement transition approaches.
—Wes Moss, Forbes.com, 22 July 2025
Genetic and environmental influences on sleep quality, ability to settle, and crying duration in 2- and 5-month-old infants: A longitudinal twin study.
—Daniella Gray, MSNBC Newsweek, 8 July 2025
Likewise, the background blur is very clean and free of color fringing (longitudinal chromatic aberration) in the fall off between focus and blur.
—PC Magazine, 8 June 2025
See All Example Sentences for longitudinal
Cite this Entry
“Longitudinal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/longitudinal. Accessed 5 Aug. 2025.
Copy CitationKids Definition
longitudinal
adjective
lon·gi·tu·di·nal
ˌlän-jə-ˈt(y)üd-nəl
-ᵊn-əl
1
: of or relating to length
2
: placed or running lengthwise
longitudinally
adverb
-ē
Medical Definition
longitudinal
adjective
lon·gi·tu·di·nal
ˌlän-jə-ˈt(y)üd-ᵊn-əl, -nəl, British also ˌläŋ-gə-ˈtyüd-
1
: of, relating to, or occurring in the lengthwise dimension
a longitudinal bone fracture
2
: extending along or relating to the anteroposterior axis of a body or part
a trypanosome which reproduces by longitudinal fission
3
: involving the repeated observation or examination of a set of subjects over time with respect to one or more study variables (as general health, the state of a disease, or mortality)
a longitudinal study of heart transplant recipients over a five-year period
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