Fourth means coming after third in order or position. When you line up four people, the fourth person is the one at the end. In a race with many runners, finishing fourth means three runners crossed the finish line before you.

You use fourth when counting things in sequence: the fourth grade comes after third grade, the fourth chapter follows the third chapter, and the fourth inning in baseball comes after the third. If someone asks for a fourth helping of dessert, they've already had three servings.

Fourth can also mean one of four equal parts, which mathematicians write as 1/4 or call “one quarter.” If you split a pizza into four equal slices, each slice is one fourth of the whole pizza. When you hear “a fourth of the class,” it means 25% of the students, since four fourths make a whole.

Americans also use the Fourth as shorthand for the Fourth of July, Independence Day, when the United States celebrates its independence from Britain in 1776. When someone mentions their Fourth of July plans, they're talking about celebrating this important holiday with fireworks, barbecues, and parades.