The term, longitudinal means "along the major (or long) axis" as opposed to latitudinal which means "along the width", transverse, or across.
See also: longitude
In anatomy, the longitudinal plane is either the coronal plane or sagittal plane. Longitudinal waves are waves that have vibrations along or parallel to their direction of travel that is waves in which the motion of the medium is in the same direction as the motion A longitudinal study is a Correlational research study that involves repeated observations of the same items over long periods of time - often many decades Longitude (ˈlɒndʒɪˌtjuːd or ˈlɒŋgɪˌtjuːd symbolized by the Greek character Lambda (λ is the east-west Geographic coordinate measurement A coronal plane (also known as the frontal plane) is any vertical plane that divides the body into Anterior and Posterior (belly and back sections A sagittal plane of the human body is an imaginary plane that travels from the top to the bottom of the body dividing it into left and right portions