86 is indeed a light novel. It gained popularity as such and then branched out into manga. The light novel typically offers more detailed character development and in-depth exploration of the story's themes compared to the manga adaptation.
Light novels usually referred to a type of light novel, also known as light novels, juvenile novels, or ACG novels. Its main feature was that it used comics, animation, games, and other ACG cultural elements as inspiration to simplify and reorganize the story, character images, and other elements, presenting a reading habit and reading experience different from traditional novels. Therefore, although light novels were usually based on novels, they usually included a large number of manga, animation, games, and other elements of ACG culture.
Radiant is primarily a manga. It features detailed illustrations and a captivating plot that has attracted a wide audience. The manga version has a dedicated fan base.
No, they're not the same. Light novels have more text and focus on storytelling through prose, while manga is a visual medium with pictures and speech bubbles.
Monogatari started as a light novel. The success of the light novels led to manga adaptations and other media expansions. But its roots are in the light novel format.