The hentai genre can be divided into numerous subgenres, the broadest of which encompasses heterosexual and homosexual acts. Hentai that features mainly heterosexual interactions occur in both male-targeted (ero) and female-targeted form. Those that feature mainly homosexual interactions are known as yaoi (male-male) and yuri (female-female). Both yaoi and, to a lesser extent, yuri, are generally aimed at members of the opposite sex from the persons depicted. While yaoi and yuri are not always explicit, their pornographic history and association remain. Yaoi's pornographic usage has remained strong in textual form through fanfiction The definition of yuri has begun to be replaced by the broader definitions of "lesbian-themed animation or comics".