mathematical concept of a singleton English 要素が一つの集合 https://en.wikipedia.org/wiki/Singleton_(mathematics) singletons singletons English singleton singleton English mathematical concept of a singleton singletons singleton type mathematical concept of a singleton singleton English English singleton singleton conjunto unitario mathematical concept of a singleton 要素が一つの集合 singleton 要素が一つの集合 conjunto unitario mathematical concept of a singleton 要素が一つの集合 singletons 참고 : http://en.wikipedia.org/wiki/Singleton_(mathematics) mathematical concept of a singleton singletons singleton