In a paper you see something like

f = m * a

and then a paragraph saying that f is force, m is mass, and a is acceleration. But in a program, you can have longer, more meaningful variable names. Why not use them?

Edit: let me use some actual apl to make my point clearer. In apl, if you want a vector of numbers, you use ι. So the command

ι 5

gives you back

1 2 3 4 5 

But some keyboards don't have that fancy character, so you can say iota instead. But if you are going to use a word, why not something that says more about what it does? ι5 is much shorter than range(5) but that only really matters if space is a premium. I'd only prefer the first one if my terminal is like ten characters wide.