The meaning of a chéngyǔ usually surpasses the sum of the meanings carried by the four characters, as chéngyǔ are generally meant to convey the message or moral of the myth, story or historical event from which they were derived. Thus, even after translation into modern words and syntax, chéngyǔ in isolation are often unintelligible without additional explanation. Since they often contain a classical allusion, known as a "diǎngù" (), elementary and secondary school students in greater China learn chéngyǔ as part of the classical curriculum in order to study the context from which the chéngyǔ was born.