"comparison" Vertical is the opposite to horizontal, and it means up and down. Upright is something which could be on it's side, like a lamp post is standing upright, if others beside it, were yet to be placed in to the ground, they wouldn't be upright yet. The posts on the ground would be lying horizontal, the post placed in to the ground would be standing vertically. The difference between the 2 types of posts would be that one was upright and the other one wasn't. There is little difference between vertical and upright, but vertical is always vertical, whereas upright suggests that perhaps it wasn't upright once, or it may not be in the future. I wonder if vertical and upright are synonyms?? Help Teachers!? :D