Very informal words, phrases, etc commonly used in speech, esp between people from the same social group of who work together, not considered suitable for formal contexts and often not in use for long.

• 而成语是人们长期以来习用的、简洁精辟的定型词组或短语。在使用过程中,并没有明显的场合之分。所以我个人认为它不等同于成语。