Idiom dictionary.

An idiom dictionary is a reference book that lists and explains commonly used idiomatic expressions in a particular language. Idioms are phrases or expressions whose meanings cannot be understood from the individual words alone. These expressions often have cultural or historical origins and are used to convey a specific meaning or message. The dictionary provides definitions, examples of usage, and sometimes the history and origin of each idiom. It is a useful tool for anyone learning a new language or trying to improve their communication skills in a given language.