Use the noun bias to mean a preference for one thing over another, especially an unfair one.
Some biases are completely innocent: "I have a bias toward French wines." But most often, bias is used to describe unfair prejudices: "The authorities investigated a case involving bias against Latinos." It is also a verb meaning "to show prejudice for or against," as in "They claimed the tests were biased against women." (In British English, it takes an extra S in the forms biassed and biassing.) The word goes back at least to Old Provençal, a former language of southern France, in association with the sport of lawn bowling, where it referred to the tendency of a ball to roll in one direction or the other.