Chengyu (simplified Chinese:成语; traditional Chinese:成語, pinyin: chéngyǔ, lit. "set phrases") are a type of traditional Chinese idiomatic expression, most of which consist of four characters. Chengyu were widely used in Classical Chinese and are still common in vernacular Chinese writing and in the spoken language today. According to the most stringent definition, there are about 5,000 chengyu in the Chinese language, though some dictionaries list over 20,000.