Chebyshev's bias

Etymology
From, the discoverer.

Proper noun

 * 1) The phenomenon that most of the time, there are more prime numbers of the form 4k + 3 than of the form 4k + 1 up to n.
 * 2) The phenomenon that if $$a$$ is a quadratic residue modulo $$q$$ and $$b$$ is a quadratic nonresidue modulo $$q$$, then $$\pi(x;b,q) > \pi(x;a,q)$$ occurs more often than not