In other words, an infinite set *S* that is a subset of another infinite set *L*, is **almost** *L* if the subtracted set *L*\\*S* is of finite size.

This is conceptually similar to the *Almost everywhere* concept of Measure theory.

Examples:

- The set is almost
**N**for any*k*in**N**, because only finitely many natural numbers are less than*k*. - The set of prime numbers is not almost
**N**because there are infinitely many natural numbers that are not prime numbers.