Definition:Greatest Common Divisor/Integers

Definition
Let $a, b \in \Z: a \ne 0 \lor b \ne 0$.

Definition 2
This is denoted $\gcd \set {a, b}$.

When $a = b = 0$, $\gcd \set {a, b}$ is undefined.

In the above, $\divides$ denotes divisibility.

General Definition
This definition can be extended to any (finite) number of integers.

Also see

 * Equivalence of Definitions of Greatest Common Divisor


 * Existence of Greatest Common Divisor


 * Elements of Euclidean Domain have Greatest Common Divisor where it is shown that any two GCDs of $a$ and $b$ are associates.

Thus it can be seen that for any two GCDs $d$ and $d'$ we have that $d = \pm d'$.