The addition of a meaning element (radical) in creating new Chinese characters
(This is a side note to the page The Chinese Writing System)
The ancient case of the character for 'dustbin' (其) being borrowed to write the word for 'other', and the subsequent attempt to disambiguate the writing of the two words by creating the character 箕specially for 'dustbin', is a telling one.
Originally, the rebus principle was applied, whereby a character was pressed into service to write another, phonetically similar form. (The two forms 其 and 箕 are pronounced differently in the modern language -- qí and jī -- and were possibly different in ancient times, although obviously close enough that the character was borrowed to write the other word.) An example of the rebus principle from English would be to write 'I' with the picture of an eye , or to write 'belief' with the picture of a bee and a leaf. The only common element is the pronunciation, with no commonality in meaning. By applying this principle, Chinese started on the path towards representing speech phonetically.
However, when the bamboo radical ⺮ was added to distinguish 箕 jī from 其 qí, the trend was reversed. A meaning element was again introduced to distinguish different characters. Huge numbers of characters were eventually created through the use of radicals as semantic markers. The result was, in effect, a 're-semantification' of Chinese characters.
Interestingly, some words may be written in ways that preserve both stages of the process -- a phonetic form, and a form consisting of a phonetic element plus a semantic element. The word cānggéng, meaning 'oriole', is one such word. Cānggéng can be written either 倉庚 / 仓庚, which represents the sound only, or 鶬鶊 / 鸧鹒, where the radical for 'bird' (鳥 / 鸟) is added to both characters to clarify the meaning.
The two different ways of writing cānggēng are a graphic illustration of what must have been a historic transition. The older writing, 倉庚 / 仓庚, seems to indicate a trend towards a phonetic representation. The addition of the bird radical in 鶬鶊 / 鸧鹒 restores the semantic element, reviving the idea that all characters should show a meaning.
Cānggēng is interesting for another reason. It is one of the relatively small class of words in Chinese that is inherently polysyllabic (see the Chinese Writing System). This includes words like 葡萄 pútáo 'grape' and 玫瑰 méiguì 'rose'. Both characters in each pair share the same meaning radical, 艹 'grass' in the first, 𤣩 'jade' in the second.
It has been suggested that many of the inherently polysyllabic forms (including both pu2tao2 and mei2gui4) were originally loanwords from foreign languages. The creation of special characters for these words contrasts with the purely phonetic representation of foreign loanwords in modern Chinese (see Chinese Writing System). Were foreign loanwords to be given meaningful radicals in modern Chinese the results might be very interesting.
For example, the word tǎnkè '(military) tank', borrowed from English, is normally rendered phonetically as 坦克 tǎnkè. The two characters literally mean 'broad and flat / calm of heart' + 'conquer'. If, say, the 'vehicle radical' 車 /车 were added to each character, the result would be / (characters which I just made up). Like the traditional examples above, each character would thus express a meaning in itself. If so, the word 反坦 fǎntǎn (anti-tank), which literally means 'counter flat' or 'overturn composure', would take on an indentifiable meaning as / 'counter tank'. However, this has not been done, marking 坦克 tǎnkè very much as a foreign word.