Special name for two variables that sum to one?

Question

I'm curious if there is any special name for the variables in the following function:

$\alpha+\beta=1$,

such that each can be determined by subtracting 1 from the other. Sort of like saying $\alpha$ is the 'reciprocal' of $\beta$ ...but through subtraction by 1 instead of division by 1.

Answer 1

We might say that $\beta$ is the complement of $\alpha$ in $1$ and vice versa.