“垂直”的意思是和地面或另一条线成九十度，上下笔直。

"垂直" means at a ninety-degree angle to the ground or another line, straight up and down.

我们常说“垂直的墙”或者“两条线垂直”。

We often say "垂直的墙" (a vertical wall) or "两条线垂直" (two lines are vertical).