[lon-ji-tood-n-l, -tyood-]
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  1. of or relating to longitude or length: longitudinal measurement.
  2. extending in the direction of the length of a thing; running lengthwise: a thin, longitudinal stripe.
  3. Zoology. pertaining to or extending along the long axis of the body, or the direction from front to back, or head to tail.
  4. pertaining to a research design or survey in which the same subjects are observed repeatedly over a period of time.
  1. a longitudinal framing member, as in the hull of a ship.

Origin of longitudinal

1535–45; < Latin longitūdin- (stem of longitūdō; see longitude) + -al1
Related formslon·gi·tu·di·nal·ly, adverb
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for longitudinal

Historical Examples of longitudinal

British Dictionary definitions for longitudinal


  1. of or relating to longitude or length
  2. placed or extended lengthwaysCompare transverse (def. 1)
  3. psychol (of a study of behaviour) carried on over a protracted period of time
Derived Formslongitudinally, adverb
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for longitudinal

1706, from Latin longitudo (see longitude) + -al (1).

Online Etymology Dictionary, © 2010 Douglas Harper

longitudinal in Medicine


  1. Running in the direction of the long axis of the body or any of its parts.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.