why MVC and singleton both are "design pattern"?

Every literature that is searched said that "MVC - is a design pattern assigns..." and the same such pattern as Singleton describes as "a software design pattern".

But WHY? This is different things that specify concepts on different levels of developing. In one MVC project you can have few Singleton, Factory and Unit of Work for example. But MVC and all this patterns still will be called "design patterns".