An idiom is a phrase, a common saying, or a string of words, that gains its meaning from the combination of all of its words. Take away one of the words, and the phrase may suddenly lose its meaning. Because of their linguistically complex and colourful nature, idioms are almost never translated literally or word for word.

One of the real difficulties that automated translation systems (and not unsurprisingly, foreign-language speakers learning English) face is interpreting and understanding the real messages conveyed by certain language constructs. Idioms often lack context and it’s difficult for both computers and new language learners to understand what’s really being said.