The zì is mostly disyllabic, i.e., comprises two characters, and is usually based on the meaning of the míng or given name. Yan Zhitui (顏之推) of the Northern Qi Dynasty believed that while the purpose of the míng was to distinguish one person from another, the zì should express the bearer's moral integrity.
The relation which often exists between a person's zì and his míng can be seen in the case of Mao Zedong whose zì was Rùnzhī ((). These two characters share the same radical - 氵, which signifies water. Both characters can mean 'to benefit' or 'to nourish'.
Another way to form a zì is to use the homophonic character zǐ - a respectful title for a male - as the first character of the disyllabic zì. Thus, for example, Gongsun Qiao's zì was: Zǐchǎn ((), and Du Fu's: Zǐméi (子美).
It is also common to construct a zì by using as the first character one which expresses the bearer's birth order among male siblings in his family. Thus Confucius, whose actual name was Kǒng Qiū (孔丘), was given the zì Zhòngní (仲尼), where the first character zhòng indicates that he was the second son in his family. The characters commonly used are bó (伯) for the first, zhòng (仲) for the second, shū (叔) for the third, and jì (季) typically for the youngest, if the family consists of more than three sons.
The use of zì began sometime during the Shang Dynasty and slowly developed into a system, which became most widespread during the succeeding Zhou Dynasty . During this period, women were also given zì. The zì given to a woman was generally composed of a character indicating her birth order among females siblings and her surname. For example, Mèng Jiāng (孟姜) was the eldest daughter in the Jiāng family.
Prior to the 20th century, sinicized Koreans, Vietnamese, and Japanese were also referred to by their zì.
The zì of some famous people:
| Family name | Given name | Zì | |
|---|---|---|---|
| Laozi | Lǐ | Ěr | Bó Yáng |
| Confucius | Kong | Qiu | Zhòngní |
| Sima Yi | Sima | Yi | Zhòngdá |
| Zhuge Liang | Zhuge | Liang | Kongming |
| Li Bai | Li | Bai | Taibai |
| Sun Yat-sen | Sun | Deming | Zaizhi |
| Mao Zedong | Mao | Zedong | Runzhi |
| Yue Fei | Yue | Fei | Pengju |