Three is the number that comes after two and before four. If you have two apples and someone gives you one more, you now have three apples. In math, we write it as 3 or sometimes III in Roman numerals.

Three shows up everywhere in stories, sayings, and traditions. Fairy tales often feature three wishes, three little pigs, or three bears. Baseball gives batters three strikes. A triangle has three sides. Many jokes and stories follow a pattern of three, and speeches often list things in threes because our brains find that pattern satisfying and memorable.

The word can also mean “a group of three things or people,” like when you say “the three of us” went to the park. Scientists have discovered that humans can instantly recognize groups of one, two, or three objects without counting, but we have to count anything larger. This might explain why three feels like such a natural, comfortable number to us.