Bias: A prejudice or leaning that may aim to influence judgments in an unfair manner; slant; prejudice.
Also known as "unconscious bias" or "covert bias"
Bias starts with you. Learn about your own bias and how it compares with others. Tools provided by AllSides to rate your own bias. compare your leanings with the rest of America, and much more.
This puzzle by The New York Times exposes a particular kind of confirmation bias.