Pianpang

Pianpangs (Chinese: 偏旁; pinyin: piānpáng; lit. 'side side') are components in Chinese character internal structures. A compound character is normally divided into two pianpangs according to their relationship in sounds and meanings. Originally, the left side component of the character was called pian, and the right side pang. Nowadays, it is customary to refer to the left and right, upper and lower, outer and inner parts of compound characters as pianpangs.
Radicals (部首) are indexing components of Chinese characters, and are usually pianpangs representing the meanings of the characters.
There are three categories of pianpangs in modern Chinese characters:
In pianpang analysis, modern Chinese compound characters are formed by the following combinations.
Semantic-semantic characters (表意字; biǎoyìzì), or Compound ideographs (会意字; 會意字; huìyìzì, 'joined meaning character'), combine two or more semantic pianpangs to indicate the meaning of the character. For example,
Phonetic-phonetic characters (表音字; biǎoyīnzì) are composed of phonetic pianpangs. For example,
Form-form characters (记号字; 記號字; jìhàozì) are composed of pure form pianpangs, which neither represent the sound nor the meaning of the characters. For example:
Semantic-phonetic characters (形声字; 形聲字; xíngshēngzì) consist of semantic and phonetic components. For example:
Semantic-form characters (义记字; 義記字; yìjìzì) are composed of semantic components and pure form components. Many of these characters were originally semantic-phonetic characters. Due to subsequent changes in the shape or pronunciation of the phonetic components or the characters, the phonetic components could not effectively represent the pronunciation of the character and became pure form. For example:
Phonetic-form characters (音记字; 音記字; yīnjìzì) are composed of phonetic components and pure form components. They mostly came from ancient semantic-phonetic characters, where the semantic components lost their functions and became pure form. For example,
Pianpangs appear in different positions of Chinese characters, including:
Some variant characters have the same pianpangs arranged in different ways. For example,
Pianpangs and radicals are components. The three concepts of pianpangs (偏旁), radicals (部首) and components (部件) often get confused among Chinese language learners.
Pianpangs are internal structural components. A compound character is normally divided into two pianpangs in internal structure, but only has one radical, usually the semantic pianpang. For example, character 江 is decomposed into pianpang 氵 and 工, where semantic 氵(水, water) is the radical.
Radicals are indexing components used for sorting and retrieving Chinese characters. According to the glyph structure of Chinese characters, the common components of a group of characters are selected as their radical. For example, "江河溪流海洋涌..." share radical 水.
In addition to radicals and pianpangs, a character may have other components. For example, character 福 is divided into pianpangs 示 and 畐, where semantic 示 is the radical. And 畐 can be further decomposed into three primitive components 一, 口 and 田 in Chinese character external structures.
The following table is based on the tables of pianpangs and bushous from Xiandai Hanyu Cidian and Xiandai Hanyu Guifan Cidian (现代汉语规范词典), including the frequently used pianpangs which exist in the Unicode character set. (Character Pianpangs are usually called by the sounds of the characters, and are not included in the table.)