Is ecchi used for humor or is it sexually playful? The definition of ecchi is sexually playful, right? But I heard it is almost always used for humor. Can someone explain please?
According to Wikipedia the definition of ecchi is:

Ecchi (エッチ etchi?, pronounced [et.tɕi]) is an often used slang term in the Japanese language for playfully sexual actions. As an adjective, it is used with the meaning of &quot;sexy&quot;, &quot;dirty&quot; or &quot;naughty&quot;; as a verb, ecchi suru (エッチする), with the meaning to have sex; or as a noun, to describe someone that is seen as lecherous. It is perhaps softer than the Japanese word ero (エロ　from Eros), and does not imply perversion in the way hentai does.
The word ecchi has been adopted by fans of Japanese media to describe works with sexual overtones. In Japanese, the word ecchi is often used to describe a person's conduct, but in fandom, 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 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.

This imply's that it can be used for a number of situations including those that are humorous or sexually playful.