megszámlálhatóság
Megszámlálhatóság, a set theory concept, refers to the property of a set whose elements can be put into a one-to-one correspondence with the natural numbers. In simpler terms, a set is countable if its elements can be listed in an infinite sequence, even if the set itself is infinite. This means that we can assign a unique natural number (0, 1, 2, ...) to each element in the set, and every element will eventually be assigned a number.
The set of natural numbers itself is the archetypal example of a countably infinite set. Other examples
A set that is not countable is called uncountable. The most famous example of an uncountable set