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
In addition to longitudinal and transverse waves, a type of wave where each of the particles involved underwent motion in what appeared to be a uniformly circular path — a surface wave — was discovered.
—
Big Think, 7 May 2026
The bark is smooth and slate-gray with distinctive white longitudinal stripes that become more fissured and rough as the tree matures.
—Sj McShane, Martha Stewart, 4 May 2026
Greater weight should be given to longitudinal treatment records and the opinions of treating mental health professionals.
—Jeffrey Freedman, Sun Sentinel, 27 Apr. 2026
Artificial intelligence could reason over a person’s longitudinal history rather than isolated snapshots.
—Celina Yong, STAT, 16 Apr. 2026
See All Example Sentences for longitudinal
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Big Think, 7 May 2026
The bark is smooth and slate-gray with distinctive white longitudinal stripes that become more fissured and rough as the tree matures.
—Sj McShane, Martha Stewart, 4 May 2026
Greater weight should be given to longitudinal treatment records and the opinions of treating mental health professionals.
—Jeffrey Freedman, Sun Sentinel, 27 Apr. 2026
Artificial intelligence could reason over a person’s longitudinal history rather than isolated snapshots.
—Celina Yong, STAT, 16 Apr. 2026
See All Example Sentences for longitudinal
Cite this Entry
“Longitudinal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/longitudinal. Accessed 9 May. 2026.
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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