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

The current study itself calls for longitudinal research to determine whether the associations seen at age 22 persist into later adulthood. — Paul McClure 23, New Atlas, 23 Aug. 2026

The results showed that the collagen fibrils and hydroxyapatite nanoparticles orient themselves along the tusk’s longitudinal axis, so there is a consistently high degree of anisotropy at all scales. — Jennifer Ouellette, ArsTechnica, 18 Aug. 2026

Some estimates were too imprecise to support a firm conclusion, and previous longitudinal studies have reported links between loneliness, isolation and physical illness. — The Conversation Us, Scientific American, 8 Aug. 2026

The Permanente Medical Group (TPMG) published a longitudinal analysis tracking an enterprise-wide ambient AI rollout across 7,260 physicians over a 63-week period. — Pat Williams, Forbes.com, 4 Aug. 2026

Word History

First Known Use

15th century, in the meaning defined at sense 2

Phrases Containing longitudinal

• longitudinal wave

Rhymes for longitudinal

• altitudinal
• attitudinal
• latitudinal

Kids 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

-ē

adverb

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

longitudinally

-ē 

adverb