Carnival denotes the pre-Lenten festival season observed across Catholic and, in some regions, Orthodox Christian cultures, running for a period of variable length that always ends precisely on Shrove Tuesday, the final day before Ash Wednesday opens the fasting and penitential season of Lent, so the whole season's length and dating are fixed each year entirely by the moveable date of Easter rather than by a calendar date of its own. Public masquerade, elaborate costume, feasting on foods later restricted during Lent, and a temporary, sanctioned inversion of ordinary social and moral restraint are common across nearly every regional form the festival takes, even where the specific customs, music and public spectacle differ enormously from one Carnival tradition to the next.
The name itself is widely though not universally derived from a Latin phrase referring to the removal of meat, tying the festival's excess directly to the dietary restriction it immediately precedes. The final day, Shrove Tuesday, carries its own local names tied to the same theme of using up restricted foods before the fast, including Mardi Gras, fat Tuesday, and pancake day in parts of the English speaking world, where eggs, milk and fat traditionally could not be kept through Lent and so were used up in one last dish immediately before it began.