longitudinal

Etymology

From Middle English longitudinal, from Latin longitūdin-, oblique stem of longitūdō (“length, longitude”), equivalent to longitude + -al.

adj

1. Relating to length, or to longitude.
2. Running in the direction of the long axis of a body.
   The units have transverse seats, two and three astride the passageway with single or double longitudinal seats alongside the two entrance vestibules in each car. 1960 November, “New electric multiple-units for British Railways: Glasgow Suburban”, in Trains Illustrated, page 660
   The third rotation is about the longitudinal axis of the thigh. 2008, Youlian Hong, Roger Bartlett, editors, Routledge Handbook of Biomechanics and Human Movement Science, Routledge, page 165
   Unlike the older trains, the new units have walk-through carriages and longitudinal rather than transverse seating. February 22 2023, Paul Stephen, “TfL reveals first of new B23s for Docklands Light Railway”, in RAIL, number 977, page 12
3. Forward and/or backward, relative to some defined direction.
4. (sciences and social sciences, of a study) Sampling data over time rather than merely once.
   longitudinal studies
   Examining national longitudinal data, Mossakowski has found that people who were unemployed for long periods in their teens or early 20s are far more likely to develop a habit of heavy drinking (five or more drinks in one sitting) by the time they approach middle age. 2010-03-01, Don Peck, “How a New Jobless Era Will Transform America”, in The Atlantic

noun

1. Any longitudinal piece, as in shipbuilding etc.
2. (rail transport) A railway sleeper lying parallel with the rail.