纵向：longitudinal 来自于longitude经度

纵的；纵向的
going downwards rather than across

The plant's stem is marked with thin green longitudinal stripes.

这种植物的茎上长有绿色细长条纹。

e.g. The insect's back is black with yellow longitudinal stripes.

vertical

(of a line, pole, etc. 线、杆等) 竖的；垂直的；直立的
going straight up or down from a level surface or from top to bottom in a picture, etc.

the vertical axis of the graph

图的纵轴

e.g. the side of the cliff is almost vertical

“纵向的”和“垂直的”意思还是有区别的

横向：lateral，可能来自于latitude纬度

侧面的；横向的；向侧面移动的
connected with the side of sth or with movement to the side

the lateral branches of a tree

树的侧枝

the lateral axis of an airplane

horizontal

水平的；与地面平行的；横的
flat and level; going across and parallel to the ground rather than going up and down

horizontal lines

横线

The line on the graph was nearly horizontal, indicating little growth over the fiscal year.

“横向的”和“水平的”差别还挺明显的

** 单词释义和每个单词第一个例句来自于百度翻译的牛津词典；每个单词第二个例句来自于Merriam-Webster: America's Most Trusted Dictionary