Prime Number

a number which can be written as a product of whole numbers in only one way, itself times 1. For example, 13 is a prime number because it can be written only as 13 - 1.

Composite Number

a number which is "composed" of other numbers in that it can be written as a product of whole numbers in more than one way. For example, 18 is a composite number because it can be written as 18 - 1, 9 - 2, or 3 - 6.

Factoring

the process of writing composite numbers as products of other numbers.

Prime Factored Form

the unique factored form of a number which consists only of prime numbers. For example, the prime factored form of 12 is 2 - 2 - 3.

Eratosthenes' Sieve

the chart of numbers we use to "sift" the prime numbers out from all numbers. It was named for the Greek mathematician who designed the process.