Stably free module

Symbol-free definition
A module over a commutative unital ring is said to be stably free if there exists a free module with which its direct sum is again a free module.

Definition with symbols
A module $$M$$ over a commutative unital ring $$R$$ is said to be stably free if there exists a free $$R$$-module $$F$$ such that $$M \oplus F$$ is again free.

Stronger properties

 * Free module

Weaker properties

 * Projective module
 * Flat module