CJK characters
Chinese is written almost exclusively in Chinese characters. It requires over 3,000 characters for general literacy, but up to 40,000 characters for reasonably complete coverage. Japanese uses fewer characters — general literacy in Japanese can be expected with 1,945 characters. The use of Chinese characters in Korea is becoming increasingly rare, although idiosyncratic use of Chinese characters in proper names requires knowledge (and therefore availability) of many more characters. However, even today, students in South Korea are taught 1,800 characters.
Chengyu
Chengyu () 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 chéngyǔ in the Chinese language, though some dictionaries list over 20,000. Chéngyǔ are considered the collected wisdom of the Chinese culture. Through the insights learned from chéngyǔ, you'll discover the experiences, moral concepts, or admonishments from the older generations of Chinese. Nowadays, chéngyǔ still plays an important role in Chinese conversations and education. It is therefore important to know some common chéngyǔ as you learn the language.