Hentai

Manga, hentai, anime... are they all the same?

In Japaneze language word "hentai" carries negative conotation. Literally it's combination of two words - strange/weird and appearence.  It's mostly used in sexual contest to describe something that's bizzare or perverted.

On the other hand word manga and word anime, when standing alone, are complete mainstream without any porn ingredients. Manga means "comic book" and anime means "animated cartoon". Therefore when you join them with word hentai you get porn/bizzare/adult/sex comics and adult cartoon.

Both mainstream and adult manga and anime were popular in Japan for decades before they achieved worldwide popularity.