Greatest common divisor (GCD)
The largest whole number that divides two or more integers exactly.
The greatest common divisor (GCD), also called the greatest common factor, is the largest positive integer that divides each of the given numbers without a remainder. It is most efficiently found with the Euclidean algorithm. The GCD is used to reduce fractions to lowest terms and, together with the least common multiple, relates by GCD × LCM = the product of the two numbers.
Example: The GCD of 12 and 18 is 6, so 12/18 reduces to 2/3.