longitudinal

/lɑndʒɪˈtudɪnəl/

/lɒndʒɪˈtudɪnəl/

Use the adjective longitudinal to describe something that takes place over a long period of time, like a study of the lifetime eating habits of people who live on islands.

Sociologists and other scientists use the word longitudinal when they're talking about long-term research. Geographers also describe things as longitudinal, but instead they mean something that relates to the east-west measurement across the Earth. When doctors use the word, it's in yet another way, describing muscles or other body parts that run lengthwise, rather than up-and-down. Longitudinal comes from the Latin word longitudo, "length or duration."

Definitions of longitudinal

1. adjective

   relating to lines that bisect the globe through the poles
   “longitudinal reckoning by the navigator”
2. adjective

   running lengthwise
   “a thin longitudinal strip”

   “longitudinal measurements of the hull”

   synonyms:

   lengthways, lengthwise

   running or extending in the direction of the length of a thing
3. adjective

   over an extended time
   “a longitudinal study of twins”

   synonyms:

   long

   primarily temporal sense; being or indicating a relatively great or greater than average duration or passage of time or a duration as specified