Ecchi is a slang term in the Japanese language for playfully sexual actions. As an adjective, it is used with the meaning of "sexy", "dirty" or "naughty"; as a verb, エッチする or Ｈする means "to have sex", and as a noun, it is used to describe someone of lascivious behavior. It is softer than the Japanese word ero (エロ from Eros or "erotic"), and does not imply perversion in the way hentai does.
The word ecchi has been adopted by western fans of Japanese media to describe works with sexual overtones. In western culture, it has come to be used to refer to softcore or playful sexuality, as distinct from the word hentai, which connotes perversion or fetishism. Works described as ecchi by the western fans do not show sexual intercourse or genitalia, but sexual themes are referenced. Ecchi themes are a type of fan service, and can be found in most comedy shōnen and seinen manga and harem anime.
Etymology and use in Japan
The correct transcription of the word エッチ in Hepburn notation