If $xy > 0$, then $x$ and $y$ are [insert fancy smart term for same sign]
Does "sign parity" work here?
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!
If $x$ and $y$ are real numbers, then the followings are equivalent.
I agree with user2468. Usually this is stated $x$ and $y$ have the same sign. sgn($x$)=sgn($y$) could also be used. [Weisstein, Eric W. "Sign." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/Sign.html]
Also "sign parity" would be confusing since "parity" is used to refer to even or oddness.