We can say that $p$ is the inverse of $1/p$ and vice-versa.
Is there a similarly succinct phrase for $p$ and $1-p$ (assuming $p$ to be a real between 0 and 1)?
It would be akin to negation in probability, but that seems to be specific to probabilities. I'm rather wondering if there's a succinct phrase, for example, for the relation between the ratio of the journey completed and the ratio of the journey left.