There are very few idiomatic or slang words in Esperanto, as these forms of speech tend to make international communication difficult—working against Esperanto's main goal. The suffix -ĉjo may be used to describe something in an affectionate manner, but this was defined ever since the first Esperanto dictionary and should not be considered slang.
- a lazy person who learns only a few simple Esperanto phrases such as "Bonan tagon!"
- ethos, atmosphere, "karma" (as of an Esperanto congress, etc.)
- to disappear from the Esperanto movement (named after author Kabe)
- to speak one's native language among a group of Esperanto speakers
- Esperantist. Originally, someone "who has the same idea" as another.
- verda papo
- "green pope"; one who talks at great length about the ideals of Esperanto
- nonsense (after the obsolete constructed language Volapük)