What is a Countable Set?
A set is countable if its cardinality (i.e., the number of elements it contains) is a countable infinite number, i.e., a number that can be put into a one-to-one correspondence with the natural numbers. In other words, a set is countable if it can be enumerated, or listed out, in a finite sequence.
For example, the set of natural numbers themselves is countable, because we can list them out in a sequence: 1, 2, 3, ... . The set of integers is also countable, because we can list out all the even integers, then all the odd integers, and so on.
On the other hand, the set of real numbers is not countable, because there are uncountably many real numbers, and there is no way to list them all out in a finite sequence.
I like this
I dislike this
Report a content error
Share
