Is there a way to save space on keys of JS objects?

I was just thinking about the following situation:

Let’s say we have a line definition like shown below. Here start and end are both points.

let line = {
    start: {x:0, y:0},
    end: {x:0,y:0},
    orientation: 'vertical'
}

Now imagine we have a very large array of lines, how do we save space? I know you can replace the orientation value 'vertical' with an Enum. But can you save space on the key names without reducing readability? E.g., you can replace orientation with o, but now it is no longer clear what the key stands for.

Let me know!