adj.
Pronunciation: ˌ län-j ə - ' tüd-n ə l, - ' tyüd-, - ' t(y)ü-d ə n- ə l, Brit also ˌ lä ŋ -g ə -
Function: adjective
Date: 15th century
1 : placed or running lengthwise
2 : of or relating to length or the lengthwise dimension
3 : 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