Bill Cosby's court appearance in Pennsylvania on charges of aggravated sexual assault marked the first time he has been formally charged with such a crime following revelations of many similar assaults on women.
Arraign means "to call (a defendant) before a court to answer to an indictment"; a synonym is charge.
An indictment is "an official written statement charging a person with a crime."
Arraign, like most English legal vocabulary, comes from French and ultimately from the Latin word that means "to reason" or "to talk reasonably." The same Latin root gave us other words that relate to reason and logic, such as ratio, rational, and reason.