The number four comes after three and before five. It's written as 4 in numerals and represents a quantity you encounter constantly: four legs on most chairs and tables, four sides on a square, four seasons in a year, four quarters in a dollar, four suits in a deck of cards.

Four appears in countless everyday phrases. When someone says they're on all fours, they're crawling on their hands and knees. A four-leaf clover is considered lucky because it's rare among the usual three-leaved clovers. If your teacher asks you to divide into groups of four, each group should have exactly four people.

In mathematics, four is the first composite number (meaning it's 2 × 2), which makes it useful for dividing things evenly. It's also a perfect square: 2² = 4. Musicians use four-four time as the most common rhythm in music, counting one-two-three-four repeatedly to keep the beat.

You can hear the idea of “four” in words like quarter (one-fourth of something) and quartet (a group of four musicians).