Chinese (and Japanese) characters are logographs (or syllabographs, or both) and as such stand for words (or parts of words). The classic equivalent for Chinese characters in the context of Western languages is that of the numerals 0..9. On themselves the numbers 0..9 can be read as separate words in one's language. For example in English: zero..nine. (another language would use different words of course, for example: nul..negen, mithen..deka, rei..to, etc. depending on the language). In English, a combination of numerical symbols can stand for just one word, for example 11 eleven, or 1000 thousand. Some combinations stand for compound words, like 21 twenty-one. Chinese characters operate in practice exactly like this. They represent words or parts of words.
While the numerals 0..9 strictly stand for the words zero..nine, especially the last two decades it has become quite unremarkable to use 0..9 not for the numerals, but for different words (or parts of words) that happen to have the same pronunciation as a given number (in phrases like ‘talk 2 me’ or ‘wait 4 me’ and much more). This so called ‘rebus usage’ (paronomasia) was actually quite common in ancient China as well. For example, the character 勿 was originally devised to stand for a word meaning ‘animal, creature, thing’ and may have been pronounced something like wu. However, some time after having created 勿 to stand for wu ‘animal’ the scribes apparently realized that they could use 勿 just as well to write wu ‘do not’ - and they did. Only much later the potential confusion that could arise from using the same symbol for two different words wu was resolved by adding an extra element (a determinative) to the character when the reader should read wu ‘animal’ in stead of wu ‘do not’, leading to 物. Quite a lot of Chinese characters have a similar history as 勿 and 物.¹ Also, the practice of using the symbol for one word to write another word that would be pronounced similarly is alive and well in modern times - usually to substitute a complicated character for one that is easier to write. Some of these substitutions have made in into official reforms.
An interesting difference between the numerals and Chinese characters is that, unlike the shapes of 0..9, the graphical shapes of Chinese characters are often less abstract and - at least originally - not arbitrary. Often the shape of a Chinese character is somehow suggestive of the word it stands for. A minority of Chinese characters consist of abstracted pictographs or semantic symbols or a combination thereof, but most are in fact composed of a phonetic element that hints at the pronunciation of the word and a semantic element that tries to pin down or classify the word semantically. In this respect the Chinese writing system is rather like the logographic stages of the cuneiform script of Mesopotamia and the hieroglyphic script of Egypt.² However, not in the least as a result of changes in the spoken language, in modern Chinese there often is a mismatch between the modern pronunciation or meaning of a word and the fossilised phonetic or semantic values of the character for that word. As a result in modern Chinese a significant number of characters have become arbitrary in their shape. Just as to Westerners the shapes of 8 and 9 have an arbitrary connection to the words eight and nine, there is little or no sense any more for the connection between for example 乙 and yǐ or 卸 and xiè.
1. Boltz 1994:60.
2. Both Cuneiform script and Ancient Egyptian script eventually developed into syllabic or alphabetic scripts, but Chinese avoided this final stage (Boltz, 1994).
William G. Boltz (1994) The origin and early development of the Chinese writing system. American oriental society: New Haven.