What is a fancy way to say "same sign" for two numbers? If $xy > 0$, then $x$ and $y$ are [ _insert fancy smart term for same sign_ ] Does "sign parity" work here?

A quick search in Google Books gives the following quote:

> [..] Hence, if $\Delta_{r-1}$ and $\Delta_r$ **are of opposite signs** , $\Delta_{r+1}$ and $\Delta_{r+2}$ **are of the same sign as** $\Delta_r$ [..]

You can't be smarter than H. S. M. Coxeter!