Pi is a special number that goes on forever. The symbol for this special number is a Greek letter “π”. To keep the math simple, we say π is 3.14. Pi is used to find the size of circles. Pi is always the same no matter how small or big the circle is.

Because it is so special, someone thought of celebrating it. Since pi is 3.14, a physicist named Larry Shaw decided March 14th would be the perfect day. So on this day in 1988, he invited his friends to walk around in a circle and eat pies. Later, more math and science lovers celebrated Pi Day on March 14th each year. On November 26th, 2019, Pi Day was recognized (正式认定) as the International Day of Mathematics.

Pi Day is celebrated in different ways. There are games in which people try to memorize as many decimal places (小数点后位数) as they can. There are pie-eating contests. Then, at 3:14 p. m., there are special events. For example, people get free pies at some parties.

Today, Pi is not just a number.