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.
Written Chinese
From the late Shang Dynasty, Chinese writing evolved into the form found in cast inscriptions on Chinese ritual bronzes made during the Western Zhou Dynasty (c 1066–770 BC) and the Spring and Autumn period (770–476 BC), a kind of writing called 金文 "jīnwén" "metal script". Jinwen characters are less angular and angularized than the oracle bone script. Later, in the Warring States period (475–221 BC), the script became still more regular, and settled on a form, called 六國文字/六国文字 "liùguó wénzì" "script of the six states", that Xu Shen used as source material in the "Shuowen Jiezi". These characters were later embellished and stylized to yield the seal script, which represents the oldest form of Chinese characters still in modern use. They are used principally for signature seals, or chops, which are often used in place of a signature for Chinese documents and artwork. Li Si promulgated the seal script as the standard throughout the empire during the Qin dynasty, then newly unified.