Graphic novel
Technically, a graphic novel is an actual (bound rather than stapled) book containing a complete comic story that was always intended to be told in the longer format.
Contrast with a trade paperback, which was originally divided up into shorter episodes sold as individual comic books, and then later on grouped together into a single volume.
Colloquially, trade paperbacks are increasingly also called graphic novels. Although this is technically incorrect, it's much more practical: you can hardly expect people to know how a given story was first published. In the Modern Age, comic book stories are now often written with their longer trade paperback arc in mind anyway, blurring the distinction between the two formats.
Comics: Comic book | DC Compact Comics | Graphic novel | Limited series | Masked vigilante | Modern Age | Superhero | Watchmen