/e/ (Ecchi)which can essentially mean Hentai, but, as Wikipedia puts it, the differences are:

  • Clothing that outlines the shape of the breasts, nipples, and labia, suggesting tightness of clothing and arousal.
  • Uniforms, costumes, or outfits (all tightly worn) that may be provocative, but are worn as everyday clothing by the character.
  • Bouncing of over-size breasts.
  • The common gag that is usually pulled off in anime, the "head in breasts gag" that is commonly used when a male meets a busty female and falls into her cleavage.
  • Characters who are unaware of their sexuality, appear innocent and cheerful, or sly and mischievous.
  • The groping of breasts (whether intentional or not.)
  • Clothing that is falling off or being pulled off, notably swimsuits and "sailor"-style schoolgirl uniforms.
  • Upskirt panty shots and cleavage.
  • Suggestive or phallic imagery.
  • Exaggerated sexual attributes, often on normal or petite figures to give a sense of contrast. Especially used in dōjinshi and fanart, where a character may appear more sexual than normal.
  • The occasional bare breast(s) or bottom, but the genital area is never shown.
  • Skimpy bathing suits with crotch lines showing and sides of breasts showing.
  • E.N.F (Embarrassed Nude Female): A female character fully/almost nude in public showing signs of embarrassment, humiliation or acting completely normally.