In mathematics, a composite number is any whole number greater than 1 that can be divided evenly by numbers other than 1 and itself. For example, 12 is composite because you can divide it evenly by 2, 3, 4, and 6. The number 15 is composite because it divides evenly by 3 and 5.

The opposite of a composite number is a prime number, which can only be divided evenly by 1 and itself. The number 7 is prime because nothing divides into it except 1 and 7. But 8 is composite because 2 and 4 also divide into it evenly.

Every composite number can be broken down into smaller prime numbers multiplied together. Think of composite numbers like buildings made of prime number blocks: 12 breaks down into 2 × 2 × 3, and 15 breaks down into 3 × 5. The number 1 is special: it's neither prime nor composite.

The word composite can also be an adjective that describes anything made by combining different parts or materials. A composite photograph blends multiple images together. Composite materials in engineering, like fiberglass, combine different substances to create something stronger than any single material alone.