longitudinal

adjective lon·gi·tu·di·nal \ˌlän-jə-ˈtüd-nəl, -ˈtyüd-, -ˈt(y)ü-d^ən-əl, British also ˌläŋ-gə-\

: placed or going along the long side of something

: of or relating to longitude

: done by observing or examining a group of people or things over time to study how one or two particular things about them change

Full Definition of LONGITUDINAL

: placed or running lengthwise

: of or relating to length or the lengthwise dimension

: involving the repeated observation or examination of a set of subjects over time with respect to one or more study variables

— lon·gi·tu·di·nal·ly adverb

See longitudinal defined for English-language learners

See longitudinal defined for kids

First Known Use of LONGITUDINAL

15th century

LONGITUDINALLY Defined for Kids

longitudinal

adjective lon·gi·tu·di·nal \ˌlän-jə-ˈtü-d^ən-əl, -ˈtyü-\

Definition of LONGITUDINAL for Kids

: placed or running lengthwise <longitudinal stripes>

— lon·gi·tu·di·nal·ly adverb

Medical Dictionary

longitudinal

adjective lon·gi·tu·di·nal \ˌlän-jə-ˈt(y)üd-^ən-əl, -nəl, British also ˌläŋ-gə-ˈtyüd-\

Medical Definition of LONGITUDINAL

: of, relating to, or occurring in the lengthwise dimension <a longitudinal bone fracture>

: extending along or relating to the anteroposterior axis of a body or part <a trypanosome which reproduces by longitudinal fission>

: 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>

—lon·gi·tu·di·nal·ly \-ē\ adverb