Chengyu in isolation are often unintelligible to modern Chinese, and when students in China learn chengyu in school as part of the classical curriculum, they also need to study the context from which the chengyu was born.

Often the four characters reflect the moral behind the story rather than the story itself. For example, the phrase "破釜沉舟" (pò fǔ chén zhōu) literally means "break the woks and sink the boats." It was based on a historical account where General Xiang Yu ordered his troops to destroy all cooking utensils and boats after crossing a river into the enemy's territory. He won the battle because of this "no-retreat" policy. Similar phrases are known in the West, such as "burning bridges" or "Crossing the Rubicon". This particular idiom cannot be used in a losing scenario because the story behind it does not describe a failure.

Many Chinese idioms have their English equivalents. For example, 冰山一角 and 'the tip of an iceberg' share both the literal and idiomatic meanings, while 言不由衷 and 'to speak one's tongue in one's cheek' share the idiomatic meaning.