Written Chinese
Because the majority of modern Chinese words contain more than one character, there are at least two measuring sticks for Chinese literacy: the number of characters known, and the number of words known. John DeFrancis, in the introduction to his "Advanced Chinese Reader", estimates that a typical Chinese college graduate recognizes 4,000 to 5,000 characters, and 40,000 to 60,000 words. Jerry Norman, in "Chinese", places the number of characters somewhat lower, at 3,000 to 4,000. These counts are complicated by the tangled development of Chinese characters. In many cases, a single character came to be written in multiple ways. This development was restrained to an extent by the standardization of the seal script during the Qin dynasty, but soon started again. Although the "Shuowen Jiezi" lists 10,516 characters—9,353 of them unique (some of which may already have been out of use by the time it was compiled) plus 1,163 graphic variants—the "Jiyun" of the Northern Song Dynasty, compiled less than a thousand years later in 1039, contains 53,525 characters, most of them graphic variants.
Chinese characters
Although Chinese characters in Vietnam are now limited to ceremonial uses, they were once in widespread use. Until the early 20th century, Literary Chinese was used in Vietnam for all official and scholarly writing. Around the 13th century the "Nôm" script was developed to record folk literature in the Vietnamese language. The script used Chinese characters to represent both borrowed Sino-Vietnamese vocabulary and native words with similar pronunciation or meaning. In addition thousands of new compound characters were created to write Vietnamese words. This process resulted in a highly complex system that was never mastered by more than 5% of the population. Both Literary Chinese and "Nôm" were replaced in the early 20th century by Vietnamese written with the Latin-based Vietnamese alphabet.