Class S , or S kankei, abbreviated either as S or Esu (エス), is an early twentieth-century Japanese wasei-eigo term used to refer to romantic friendships between girls. The term is also used to designate a genre of girl's fiction which tells stories about the same, typically focused on senpai and kōhai relationships wherein one girl is senior in age or position to the other. The "S" is an abbreviation that can stand for "sister", "shōjo" , "sex", "schön", and "escape".

Yuri , also known by the wasei-eigo construction girls' love , is a genre of Japanese media focusing on intimate relationships between female characters. While lesbian relationships are a commonly associated theme, the genre is also inclusive of works depicting emotional and spiritual relationships between women that are not necessarily romantic or sexual in nature. Yuri is most commonly associated with anime and manga, though the term has also been used to describe video games, light novels, and literature.