Xu Shen, a researcher in the Dong Han Dynasty (25-220), analyzed the structure of the Chinese characters on the basis of the teachings of the I-Jing and the five elements, and documented his studies in the most important book on Chinese in history, called “Explaining Simple and Analyzing Compound Characters” (說文解字 shuōwén jiězì).
In his book Xu Shen divided the Chinese characters into six categories:
象形 Xiàngxíng, pictographs “depicting directly”: These display the meaning through directly depicting the appearance (for example: 山 for mountain, 人 for man, etc.);
指事 Zhǐshì, ideograms “pointing out the facts”: These are like conceptual pictographs, in that they represent an abstract idea through a picture. (for example: 一, 二, and 三 for “one”, “two”, and “three”; and 上 for “up”, 下 for “down”.)
會意 Huìyì, ideogrammic compounds “combination of meanings”: characters that consist of two or more characters with different meanings and whose contents are combined to create new characters (for example: 安 “peace” is a combination of “roof” 宀 and “woman” 女, meaning “all is peaceful with the woman at home”)
形聲 Xíngshēng, phono-semantic compounds “form and sound”: characters which consist of one sound component and one meaning component. (for example 媽 mā means “mother”, the right component 馬 is pronounced mǎ and means “horse”—it indicates the phonetic element—while the left component is 女 (nǚ, meaning “woman”), and this gives the meaning. The meaning component is often a “radical” (one of about 200 ‘building blocks’ of characters which make up the Chinese written language). About 90 percent of all Chinese characters fall in the Xíngshēng group.
假借 Jiǎjiè, phonetic-loans “under false name”: the reasoning behind these characters is slightly more complex, and relates to the historical development of written Chinese. In ancient China, one character would often be used for more than one meaning. But as the character was passed around, the more common character would end up “borrowing” the earlier one. For example, 來 was the pictogram for “wheat”, but it was also used for the verb “to come”. Eventually the more common “to come” became the default meaning of the character 來, and a new character for “wheat”, 麥, was established.
轉注 Zhuǎnzhù, reciprocal meaning “turn and pour”: this is a purely historic categorization, and refers to characters that have the same etymological root but which have diverged in pronunciation and meaning. 老lǎo “old” and 考kǎo “test” is a common example.