Ecchi

[Tina]

Softcore [hentai]. Often includes panty-shots, nudity, or perverted situations. Almost always used for humor. Ecchi does not describe actual sex acts.

[Mark Zuckerberg]

In anime (Japanese animation) fan circles, when you say something is ecchi you mean it is erotic, but usually not with all-out sex or anything very vulgar. Basically like hentai but more softcore.

In Japanese: comes from English letter H, possibly an abbreviation of the word hentai which means perverted/sexually deviant. Refers to the act of sex, or can refer to anything sexual in nature if used as an adjective with the -na suffix.

[Tina]

Ecchi is a word that has two related but VERY different meanings in Japanese and English respectivly.
English: Ecchi in English speaking anime fandom is considered to mean mildly perverted. It is used to describe anime and manga with panty shots, the occasional nipple, sexual humour, and other forms of fanservice but does not actualy conatain sex.
Japanese: In the Japanese usage ecchi literaly means sex. When the Japanese refer to ecchi anime they mean what English speakers would call hentai, which in Japan is used to mean pervert

[Becky]

Ecchi is the pronunciation for the letter H. It is a word for lewd or perverted and often related to [hentai] - especially in Japanese, where ecchi is slang for [hentai]. More often than not, though, ecchi is used to describe people rather than things such as [anime].

[Donald Trump]

From what I have been told and seen it seems that ecchi is a manga term to describe nudity that isnt sexually oriented whereas hentai is all about sex.

[Sarah]

The sound of H in japanese phoneme which is a shorthand for saying hentai.
The most commonly used word for sex in modern time Japan; was also used for defining erotic means across the internet by foreigners.

[Donald Trump]

When used as an insult, means You perv while [hentai] means more You sick-minded, disgusting freak

And it -does- mean lighter perversion, though western culture has twisted it.

[Britney]

Its a genere in japanese anime and manga that reffers to erotic but not abruptly sexual content. It can show full to partial nudity, including nipples, cameltoes, panty flashing, grabbing boobs, but never exposed genitals, and is often displayed in a humoresque way. The term comes from the japanese pronunciation of the letter H (pronounced eh-chi) as in Japan erotic content is rated H while in the rest of the world its more commonly rated X.
Outside of Japan its easier to understand Ecchi as softcore, non-sexual and erotic and Hentai as hardcore pornography.