可か算さん集しゅう合ごう

noun

countable set

A set whose elements can be put into a one-to-one correspondence with a subset of the natural numbers; includes finite sets and countably infinite sets.

• 整せい数すう全ぜん体たいの集しゅう合ごうは可か算さん集しゅう合ごうである。

  The set of all integers is a countable set.

• 可か算さん集しゅう合ごうの部ぶ分ぶん集しゅう合ごうも可か算さん集しゅう合ごうになる。

  A subset of a countable set is also a countable set.