Closure
Core Idea
A set of objects is considered closed under an operation if and only if the set of objects that result from applying the operation on the objects does not change. In other words, if the initial set of objects remains unchanged when the operation is applied onto the objects in the set.
Consider all the Vectors in . For a familiar definition of addition as element-wise addition and scalar multiplication as element-wise scaling, the vectors in are closed with respect to addition.