noun
Technical term used in engineering, physics, and materials science to refer to the direction along the length of an object.
この材料は長方向に強い。
This material is strong in the longitudinal direction.
長方向の伸びを測定する。
Measure the elongation in the longitudinal direction.
縦方向 also means 'longitudinal direction' or 'vertical direction', often used interchangeably with 長方向, but 長方向 emphasizes the lengthwise axis more explicitly.
Compound of 長 (long) + 方向 (direction). A straightforward technical term.